Polyester copolymer

ABSTRACT

The present disclosure is a polyester copolymer, having a number average molecular weight of equal to or more than 5000 grams/mole and having a glass transition temperature of less than 160° C., comprising:—in the range from equal to or more than 25.0 mole % to equal to or less than 49.9 mole %, based on the total amount of moles of monomer units within the polyester copolymer, of one or more bicyclic diol monomer units, wherein such one or more bicyclic diol monomer units is/are derived from one or more bicyclic diols chosen from the group consisting of isosorbide, isoidide, isomannide, 2,3:4,5-di-O-methylene-galactitol and 2,4:3,5-di-O-methylene-D-mannitol;—in the range from equal to or more than 45.0 mole % to equal to or less than 50.0 mole %, based on the total amount of moles of monomer units within the polyester copolymer, of an oxalate monomer unit; and/or—in the range from equal to or more than 0.1 mole % to equal to or less than 25.0 mole %, based on the total amount of moles of monomer units within the polyester copolymer, of one or more linear C2-C12 diol monomer units, wherein such one or more linear C2-C12 diol monomer units is/are derived from one or more linear C2-C12 diols; and/or—optionally equal to or more than 0.0 mole % to equal to or less than 5.0 mole %, based on the total amount of moles of monomer units within the polyester copolymer, of one or more additional monomer units.

FIELD OF THE INVENTION

The invention relates to novel polyester copolymers, a process for theproduction of a polyester copolymer, a composition containing apolyester copolymer, a method for manufacturing an article using apolyester copolymer, and an article obtained or obtainable by such amethod.

BACKGROUND TO THE INVENTION

In recent times a tendency has grown to obtain a variety of chemicalproducts from sustainable resources. Polymers and monomers constitute animportant part of chemical products produced in the world today, about80% of the bulk chemicals are monomers or monomer precursors. Theytherefore play a central role in the transition to a sustainablechemical industry. The majority of polymers today are produced fromfossil fuel feedstock, giving after use (via incineration ordegradation) rise to extensive greenhouse gases emissions globally. Thedevelopment of so-called sustainable, preferably partly or whollybio-based, polymers, could contribute significantly to the developmentof a more sustainable chemical industry.

In the past, work has been done to develop (partially) bio-basedpoly(ethylene terephthalate) (PET). For example in WO2013/034743 amethod for producing a bio-PET polymer is described. Such a processusing bio-based terephthalic acid or bio-based terephthalic acid ester,however, remains too expensive to date to experience commercial success.

WO2015/142181 describes a polyester comprising at least onefurandicarboxylate unit, at least one saturated, linear or branched,diol unit comprising from 2 to 10 carbon atoms and at least one bicyclicdiol unit, chosen from isosorbide, isoidide, isomannide,1,3:4,5-di-O-methylene-galactitol and 2,4:3,5-di-O-methylene-D-mannitol,characterized in that the glass transition temperature of said polyesteris greater than or equal to 90° C. Although good results are obtained,also the preparation of this polyester remains expensive and it would bean advantage to have a further, economically more attractive,alternative.

In the article of Fenouillot et al, titled “Polymers from renewable1,4:3,6-dianhydrohexitols (isosorbide, isomannide and isoidide): Areview”, published in Progress in Polymer Science Vol. 35 (2010) pages578 to 622, it is indicated that 1,4:3,6-Dianhydrohexitols, such asisosorbide (1,4:3,6-dianhydro-D-glucidol), isomannide(1,4:3,6-dianhydro-D-mannitol) and isoidide(1,4:3,6-dianhydro-L-iditol), can be derived from renewable resourcesfrom cereal-based polysaccharides. It is indicated that in the field ofpolymeric materials, these diols are essentially employed to synthesizeor modify polycondensates. Their attractive features as monomers arelinked to their rigidity, chirality, non-toxicity and the fact that theyare not derived from petroleum.

US2003/0204029 describes isosorbide-containing polyesters and a processto produce isosorbide-containing polyesters. The process described inUS2003/0204029 to produce polyesters comprises melt mixing a firstpolyester which incorporates isosorbide comprised essentially of: 45.0to 50.0 mole percent of a dicarboxylic acid component; 5.0 to 50.0 molepercent of isosorbide; 0 to 45.0 mole percent of a diol component otherthan ethylene glycol or di(ethylene glycol); and 0 to 5.0 mole percentof a polyfunctional branching agent component; with a second polyestercomprised essentially of: 45.0 to 50.0 mole percent of a dicarboxylicacid component, 45.0-50.0 mole percent of a diol component other thanisosorbide: and 0 to 5.0 mole percent of a polyfunctional branchingagent component; at a temperature and for a time sufficient to effecttransesterification, optionally followed by a finishing process. It alsodescribes a polyester comprised essentially of 45 to 50 mole percent ofa dicarboxylic acid component, 0.1 to 40 mole percent isosorbide, 10 to49.9 mole percent of another diol component and 0 to 5.0 mole percent ofa polyfunctional branching agent component. In its descriptionUS2003/0204029 mentions a long list of more than 50 dicarboxylic acidcomponents that supposedly could be used in the production of theisosorbide-containing polyesters. In passing, US2003/0204029 alsomentions oxalic acid and dimethyl oxalate as possible dicarboxylic acidcomponents, but US2003/0204029 does not provide any enabling disclosureof how any polyester can be made with such oxalic acid and/or dimethyloxalate. US2003/0204029 mentions that preferably the first polyesterincorporating isosorbide is produced through a melt polymerizationmethod. As explained below and illustrated in the examples of thepresent case, however, it is not possible to obtain anyisosorbide-containing polyester with a commercially interestingmolecular weight by melt polymerization when using the oxalic acid ordimethyl oxalate as mentioned in US2003/0204029 as a starting component.US2003/0204029 does therefore not avail society with the knowledge toprepare any polyester containing isosorbide and oxalate and hence cannotdisclose such polyester to society.

US2010/0160548 describes a process for the production of a polyester bypoly-condensation of a mixture comprising isoidide, and a dicarboxylicacid or dicarboxylic acid anhydride, wherein the reaction is performedin the melt of the monomers and wherein these monomers are notactivated. As dicarboxylic acids, aliphatic di- or polyvalent carboxylicacids having 4 to 20 carbon atoms are mentioned. Oxalic acid or anyoxalates are not mentioned.

JP2006161017 (a counterpart of WO2005/103111) is directed to theprovision of an isosorbide type biodegradable polymer which has asharply improved heat-resisting property and describes an isosorbidetype polyoxalate with a glass transition temperature (Tg) of more than160° C. It is indicated that the polyoxalate may contain an additionalrepeating unit, provided such additional repeating unit does not impaira glass transition temperature of 160° C. or more.

JP2006161017 indicates that the polyoxalate described can bemanufactured by a polycondensation reaction with the isosorbide, oxalicacid or its derivative(s), such as an oxalic-acid diester or anoxalic-acid dichloride. When the polyoxalate contains an additionalester unit as an additional repeating unit, a part of the oxalic acid ora derivative thereof is replaced with an additional acid component inthe polycondensation reaction. Also when the polyoxalate contains anadditional ester unit as an additional repeating unit, part of theisosorbide is replaced with an additional alcohol component.

In the examples of JP2006161017 an oxalic acid diphenyl ester is reactedwith isosorbide in the presence of a butyltinhydroxyoxide hydratecatalyst to prepare a poly isosorbide oxalate polymer having a glasstransition temperature of more than 160° C. The manufacture ofpolyoxalates with an additional repeating unit was not disclosed and nosuch polyoxalates with an additional repeating unit were exemplified.

The polymers of JP2006161017, having a high Tg of more than 160 degreesC., are very difficult to process in a commercial interesting manner.

It would be an advancement in the art to provide a novel polyestercopolymer, with a commercially interesting molecular weight and glasstransition temperature, partially or completely derived fromeconomically attractive monomers and/or to provide a novel economicallyattractive process for the production of such polyester copolymer. Itwould be an even further advancement if such polyester copolymer could,if so desired, be partially or completely derived fromsustainably-sourced monomers.

SUMMARY OF THE INVENTION

Such a polyester copolymer has been obtained with the polyestercopolymer according to the invention. Accordingly, the present inventionprovides a polyester copolymer, having a number average molecular weightof equal to or more than 5000 grams/mole and having a glass transitiontemperature of less than 160° C., containing:

(a) in the range from equal to or more than 25 mole % to equal to orless than 49.9 mole %, based on the total amount of moles of monomerunits within the polyester copolymer, of one or more bicyclic diolmonomer units, wherein such one or more bicyclic diol monomer unitsis/are derived from one or more bicyclic diols chosen from the groupconsisting of isosorbide, isoidide, isomannide,2,3:4,5-di-O-methylene-galactitol and 2,4:3,5-di-O-methylene-D-mannitol;

(b) in the range from equal to or more than 45 mole % to equal to orless than 50 mole %, based on the total amount of moles of monomer unitswithin the polyester copolymer, of an oxalate monomer unit;

(c) in the range from equal to or more than 0.1 mole % to equal to orless than 25 mole %, based on the total amount of moles of monomer unitswithin the polyester copolymer, of one or more linear C2-C12 diolmonomer units, wherein such one or more linear C2-C12 diol monomer unitsis/are derived from one or more linear C2-C12 diols; and

(d) optionally equal to or more than 0 mole % to equal to or less than 5mole %, based on the total amount of moles of monomer units within thepolyester copolymer, of one or more additional monomer units.

Suitably the total amount of moles of monomer units in the polyestercopolymer adds up to essentially 100 mole %, more preferably 100.0 mole%.

The oxalate monomer unit forms an economically attractive alternativefor the above mentioned furandicarboxylate unit and terephthalate unit.Furthermore the polyester copolymer can be produced in an economicallyattractive process as described below. Advantageously, as illustrated inthe examples, the novel polyester copolymer has a commerciallyinteresting molecular weight and glass transition temperature. Inaddition, if so desired, the oxalate monomer unit and/or the bicyclicdiol monomer unit(s) and/or the linear C2-C12 diol monomer unit(s) canbe obtained and/or derived from a sustainable source, as describedbelow.

Surprisingly, by varying the amount of bicyclic diol monomer unit(s) andthe amount and type of linear C2-C12 diol monomer unit(s), the glasstransition temperature (Tg) of the polyester copolymer canadvantageously be targeted to a desired value in the range from equal toor more than minus 60° C. (−60° C.), preferably equal to or more than20° C., to less than 160° C., preferably equal to or less than 150° C.and more preferably equal to or less than 140° C. The bicyclic diolmonomer unit and linear C2-C12 diol monomer unit suitably work togetherin a synergetic manner, such that conveniently the targeted Tg can beobtained.

The novel polyester copolymer according to the invention canadvantageously be used in industrial applications, such as in films,fibres, injection moulded parts and packaging materials. For example,when the polyester copolymer is targeted towards a glass transitiontemperature in the range from equal to or more than 100° C. to less than160° C., preferably equal to or less than 140° C., the polyestercopolymer can be very suitable for use in applications where a product,such as for example a film, fibre, injection moulded part or packagingmaterial, needs to be heat-resistant, for example in the case of coffeecups, microwave applications and certain medical applications. When thepolyester copolymer is targeted towards a glass transition temperaturein the range from equal to or more than −60° C. to equal to or less than100° C. or equal to or less than 80° C., the polyester copolymer can bevery suitable for use in applications where a product needs to remainresilient at low temperatures and/or needs to be able to withstand coldwithout breaking or becoming too brittle, for example in the case ofcar-bumpers or outdoor furniture. When the polyester copolymer istargeted towards a glass transition temperature in the range from equalto or more than 60° C. to equal to or less than 120° C. or equal to orless than 100° C., the polyester copolymer can be very suitable for thereplacement of poly(ethylene terephthalate) (PET) in applications suchas bottles and/or containers.

Without wishing to be bound by any kind of theory, it is furtherbelieved that the polyester copolymer according to the invention mayhave a commercially interesting oxygen-permeation degree and/or may havean improved (bio-) degradability when compared to for example PET.

In addition, this present invention conveniently provides a process forproducing such a polyester copolymer. Accordingly, the present inventionprovides a process for the production of a polyester copolymercomprising polymerizing the following monomers:

(i) in the range from equal to or more than 25 mole percent (mole %) toless than 50 mole %, based on the total amount of moles of monomers, ofone or more bicyclic diols chosen from the group consisting ofisosorbide, isoidide, isomannide, 2,3:4,5-di-O-methylene-galactitol and2,4:3,5-di-O-methylene-D-mannitol;(ii) in the range from equal to or more than 45 mole % to equal to orless than 50 mole %, based on the total amount of moles of monomers, ofone or more oxalic diesters having a chemical structure according toformula (VI):

wherein R₂ and R₃ each independently are a C3-C20 alkyl group, a C2-C20alkenyl group, a C4-C20 cycloalkyl group, a C4-C20 aryl group or aC5-C20 alkylarylgroup;(iii) in the range from equal to or more than 0.1 mole % to equal to orless than 25 mole %, based on the total amount of moles of monomers, ofone or more linear C2-C12 diols; and(iv) optionally equal to or more than 0 mole % to equal to or less than5 mole %, based on the total amount of moles of monomers, of one or moreadditional monomers.

Suitably the total amount of moles of monomers in the process adds up toessentially 100 mole %, more preferably 100.0 mole %.

In contrast to the process as described in US 2003/0204029, the use of aprocess according to the present invention advantageously allows one toprovide an oxalate-containing polyester co-polymer with a number averagemolecular weight equal to or more than 5000 grams/mole.

Conveniently the Tg of the produced polyester copolymer can be targetedto a desired value by tuning the amount of the one or more bicyclicdiols and the type and amount of the one or more linear C2-C12 diolsduring the process. Advantageously polyester copolymers with acommercially interesting number average molecular weight can be obtainedwithin commercially advantageous reaction times.

Without wishing to be bound by any kind of theory it is believed that byreplacing part of the bicyclic diols with linear C2-C12 diols, thereaction rate is advantageously increased. It is thus believed that theprocess according to the invention may allow one to produce polyestercopolymers with a certain fixed number average molecular weight within ashorter time frame compared to a process where mainly or solely bicyclicdiols are used. Or, in the alternative, it is believed that the processmay allow one to, within a certain fixed time frame, produce polyestercopolymers with a higher number average molecular weight, compared to aprocess where mainly or solely bicyclic diols are used.

As will be described in more detail below, preferably the one or moreoxalic diesters are diesters of oxalic acid and one or more alkanols,which alkanols have an acid dissociation constant (pKa) of equal to orless than 20.0, more preferably equal to or less than 15.0.

The invention further provides a polyester copolymer, preferablyobtained or obtainable by means of the above process, having a numberaverage molecular weight of equal to or more than 5000 grams/mole andhaving a glass transition temperature of less than 160° C., containingthe following repeating units:

-   -   in the range from equal to or more than 45.0 mole % to equal to        or less than 99.9 mole %, based on the total amount of moles of        repeating units within the polyester copolymer, of one or more        bicyclic diol-oxalate repeating units chosen from the group        consisting of isosorbide-oxalate, isoidide-oxalate,        isomannide-oxalate, 2,3:4,5-di-O-methylene-galactitol-oxalate        and 2,4:3,5-di-O-methylene-D-mannitol-oxalate;    -   in the range from equal to or more than 0.1 mole % to equal to        or less than 50.0 mole %, based on the total amount of moles of        repeating units within the polyester copolymer, of one or more        linear C2-C12-diol-oxalate repeating units;    -   optionally in the range from equal to or more than 0.0 mole % to        equal to or less than 5.0 mole %, based on the total amount of        moles of repeating units within the polyester copolymer, of one        or more additional repeating units;

wherein the molar ratio of bicyclic diol-oxalate repeating units tolinear C2-C12-diol-oxalate repeating units is equal to or more than 1:1,more preferably equal to or more than 1.5:1. Suitably the total amountof moles of repeating units within such polyester copolymer adds up toessentially 100 mole %, more preferably 100.0 mole %.

In addition, the invention provides a composition containing any one ofthe polyester copolymers as described above and in addition one or moreadditives and/or one or more additional polymers.

Further the invention provides a method for manufacturing an article,comprising the use of one or more polyester copolymers according to theinvention.

Still further, the invention provides an article obtained or obtainableby such a method for manufacturing an article as described above.

DETAILED DESCRIPTION OF THE INVENTION

By a “polyester” is herein understood a polymer comprising a pluralityof monomer units linked via ester functional groups in its main chain.An ester functional group can be formed by reacting an hydroxyl group(—OH), sometimes also referred to as an alkanol group, with a carboxylgroup (—C(═O)OH), sometimes also referred to as an carboxylic acidgroup. By a polyester copolymer is herein understood a polyester whereinthree or more types of monomer units are joined in the same polymer mainchain. As will be described in more detail in the claims and hereinbelow, the polyester copolymer according to the invention suitablycontains one or more bicyclic diol monomer units (as mentioned under(a)), an oxalate monomer unit (as mentioned under (b)), and one or morelinear C2-C12 diol monomer units (as mentioned under (c)). In addition,the polyester copolymer can optionally contain one or more distinctadditional monomer units (as mentioned under (d)). As mentioned below,however, it is also possible for the polyester copolymer according tothe invention to essentially or solely consist of the one or morebicyclic diol monomer units (as mentioned under (a)), the oxalatemonomer unit (as mentioned under (b)), and the one or more linear C2-C12diol monomer units (as mentioned under (c)). That is, it is possible forthe polyester copolymer to be devoid of any other additional monomerunits.

By a “monomer unit” is herein understood a unit as included in thepolyester copolymer, which unit can be obtained after polymerization ofa monomer, that is, a “monomer unit” is a constitutional unitcontributed by a single monomer or monomer compound to the structure ofthe polymer.

By a “monomer” or “monomer compound” is herein understood the startingcompound to be polymerized.

By a “Cx” compound is herein understood a compound having “x” carbonatoms. Similarly, by a “Cy” compound is herein understood a compoundhaving “y” carbon atoms. By a “Cx-Cy” compound is therefore hereinunderstood a compound having in the range from equal to or more than “x”to equal to or less than “y” carbon atoms. For the avoidance of doubt,it is therefore well possible for a Cx-Cy compound to contain more than“x” or less than “y” carbon atoms.

Herein below the monomer units will be described one by one.

The first monomer unit (as listed under (a)), may suitably comprise oneor more bicyclic diol monomer units, wherein such one or more bicyclicdiol monomer units is/are suitably derived from one or more bicyclicdiols chosen from the group consisting of

Such derived monomer unit may herein sometimes also be referred to“bicyclic diol-derived monomer unit” or simply as “bicyclic diol unit”.More preferably the one or more bicyclic diol monomer units is/are oneor more 1,4:3,6-dianhydrohexitol monomer units, wherein such one or morebicyclic diol monomer units is/are derived from one or more1,4:3,6-dianhydrohexitols. Such bicyclic diol monomer unit derived fromone or more 1,4:3,6-dianhydrohexitols can herein sometimes also bereferred to as “1,4:3,6-dianhydrohexitol-derived monomer unit” or simplyas “1,4:3,6-dianhydrohexitol unit”. More suitably the term“1,4:3,6-dianhydrohexitol monomer unit”,“1,4:3,6-dianhydrohexitol-derived monomer unit” or“1,4:3,6-dianhydrohexitol unit” may refer to monomer units chosen fromthe group of monomer units of the formulae (IIA), (IIB) and/or (IIC):

The isosorbide monomer unit exemplified in formulae (IIA) can, withinthe polyester copolymer, exist in two three-dimensional structures asexemplified in paragraphs [0021] and of JP2006161017, and bothstructures are included herein by reference.

Examples of suitable 1,4:3,6-dianhydrohexitols include isosorbide(1,4:3,6-dianhydro-D-glucidol), isomannide(1,4:3,6-dianhydro-D-mannitol), isoidide (1,4:3,6-dianhydro-L-iditol)and mixtures thereof. The most significant difference among the1,4:3,6-dianhydrohexitol isomers may be the orientation of the two“hydroxyl” groups. This difference in orientation can result indifferent orientations of the ester group in the polymer, allowing forseveral variations in spatial configuration and physical and chemicalproperties of the polymer. As indicated above, it is possible for thepolyester copolymer to contain only one isomer of1,4:3,6-dianhydrohexitol-derived monomer unit or to contain a mixture oftwo or more isomers of 1,4:3,6-dianhydrohexitol-derived monomer units,for example a mixture of monomer units derived from isosorbide and/orisomannide and/or isoidide (also sometimes referred to herein asrespectively isosorbide unit, isomannide unit and/or isoidide unit).

Preferably the one or more bicyclic diol monomer units is/are one ormore 1,4:3,6-dianhydrohexitols monomer units and preferably the molarratio of such 1,4:3,6-dianhydrohexitols monomer units to linear C2-C12diol monomer units is equal to or more than 1:1, preferably equal to ormore than 1.5:1.

Preferably, the one or more 1,4:3,6-dianhydrohexitol monomer unitsis/are derived from isosorbide and/or isoidide. More preferably,however, the polyester copolymer only contains one isomer of a1,4:3,6-dianhydrohexitol-derived monomer unit. More preferably the1,4:3,6-dianhydrohexitol-derived monomer unit is a monomer unit derivedfrom isosorbide or isoidide. Still more preferably the1,4:3,6-dianhydrohexitol-derived monomer unit is a monomer unit derivedfrom isosorbide (also sometimes referred to herein as isosorbide unit).Most preferably the polyester copolymer only contains monomer unitsderived from isosorbide and essentially no monomer units derived fromisomannide and/or isoidide.

The bicyclic diol, and especially the 1,4:3,6-dianhydrohexitol, ispreferably obtained and/or derived from a sustainable biomass material.By a biomass material is herein understood a composition of matterobtained and/or derived from a biological source as opposed to acomposition of matter obtained and/or derived from petroleum, naturalgas or coal. The biomass material can for example be a polysaccharide,such as starch, or a cellulosic and/or lignocellulosic material. Bysustainable is herein understood that the material is harvested and/orobtained in a manner such that the environment is not depleted orpermanently damaged. Sustainable biomass material may for example besourced from forest waste, agricultural waste, waste paper and/or sugarprocessing residues.

Isosorbide, isomannide and isoidide can be suitably obtained bydehydrating respectively sorbitol, mannitol and iditol.

The synthesis of these 1,4:3,6-dianhydrohexitols is well known:different routes are described, for example, in the papers by Fletcheret al. (1,4,3,6-Hexitol dianhydride, 1-isoidide, J. Am. Chem. Soc.,1945, 67, 1042-3 and also 1,4,3,6-dianhydro-l-iditol and the structureof isomannide and isosorbide, J. Am. Chem. Soc., 1946, 68, 939-41), byMontgomery et al. (Anhydrides of polyhydric alcohols. IV. Constitutionof dianhydrosorbitol, J. Chem. Soc., 1946, 390-3 and Anhydrides ofpolyhydric alcohols. IX. Derivatives of 1,4-anhydrosorbitol from1,4,3,6-dianhydrosorbitol, J. Chem. Soc., 1948, 237-41), by Fleche etal. (Isosorbide. Preparation, properties and chemistry, Starch/Staerke,1986, 38, 26-30) and by Fukuoka et al. (Catalytic conversion ofcellulose into sugar alcohols, Angew. Chem. Int. Ed., 2006, 45, 5161-3),and in U.S. Pat. No. 3,023,223.

For its part, the 2,3:4,5-di-O-methylene-galactitol can be obtained byacetalization and then reduction of galactaric acid, as described byLavilla et al. in Bio-based poly(butylene terephthalate) copolyesterscontaining bicyclic diacetalized galactitol and galactaric acid:Influence of composition on properties, Polymer, 2012, 53(16),3432-3445. For its part, the 2,4:3,5-di-O-methylene-D-mannitol can beobtained by acetalization of D-mannitol by formaldehyde, as described byLavilla et al. in Bio-Based Aromatic Polyesters from a Novel BicyclicDiol Derived from D-Mannitol, Macromolecules, 2012, 45, 8257-8266.

The polyester copolymer preferably contains in the range from equal toor more than 25.0 mole % to equal to or less than 49.9 mole %, based onthe total amount of moles of monomer units within the polyestercopolymer, of one or more bicyclic diol monomer units, preferably1,4:3,6-dianhydrohexitol-derived monomer units.

The amounts of bicyclic diol-derived monomer unit and linear C2-C12diol-derived monomer units can advantageously be targeted towards adesired Tg. For some applications the polyester copolymer is preferablya polyester copolymer containing in the range from equal to or more than25.0 mole % to equal to or less than 45.0 mole %, more preferably equalto or less than 35.0 mole %, based on the total amount of moles ofmonomer units within the polyester copolymer, of a bicyclic diol monomerunit, preferably 1,4:3,6-dianhydrohexitol monomer unit. For otherapplications the polyester copolymer is preferably a polyester copolymercontaining in the range from equal to or more than 35.0 mole % to equalto or less than 49.9 mole %, more preferably equal to or less than 45.0mole %, based on the total amount of moles of monomer units within thepolyester copolymer, of a bicyclic diol monomer unit, preferably1,4:3,6-dianhydrohexitol monomer unit. The percentages here are unitpercentages, also referred to sometimes as mole unit percentages. Thatis, the percentages are calculated in “moles” of monomer units.

The second monomer unit (as listed under (b)), suitably comprises anoxalate monomer unit. Such oxalate monomer unit may have a chemicalstructure according to formula (III):

Such oxalate monomer unit is herein sometimes also referred to as simply“oxalate unit”.

The oxalate monomer unit is preferably obtained and/or derived from asustainable source. For example the oxalate monomer may be obtainedand/or derived from a sustainable biomass material. For example, by useof fungi, such as described in the article of Liaud et al., titled“Exploring fungal biodiversity: organic acid production by 66 strains offilamentous fungi”, published in Fungal Biology and Biotechnology (2014)(published online), an oxalic acid may be produced which may beconverted into an oxalic diester by conventional means. It is, however,also possible for the oxalate monomer to be obtained and/or derived fromcarbon monoxide and/or carbondioxide (CO₂), for example by means ofelectrochemical conversion. For example WO 2014/100828 and WO2015184388describe the electrochemical conversion of CO₂ to oxalate and oxalicacid and their contents are herein incorporated by reference. Such CO₂is considered a sustainable source.

The polyester copolymer preferably contains in the range from equal toor more than 45.0 mole % to equal to or less than 50.0 mole % of anoxalate monomer unit, based on the total amount of moles of monomerunits within the polyester copolymer. As indicated above, thepercentages here are unit percentages, also referred to sometimes asmole unit percentages.

In addition to the oxalate monomer unit, one or more other dicarboxylatemonomer units may be present as optional additional monomer units, forexample in an amount from equal to or more than 0.1 mole % to equal toor less than 5.0 mole %, as described in more detail below. Preferably,however, the polyester copolymer contains essentially no such otherdicarboxylate monomer units. That is, preferably the polyester copolymeris devoid of any dicarboxylate monomer units other than the oxalatemonomer unit.

The third monomer unit (as listed under (c)), suitably comprises alinear C2-C12 diol monomer unit. Such linear C2-C12 diol monomer unitmay for example have a chemical structure according to formula (IV):

wherein R₁ is a linear organic group. Preferably R₁ is a bivalent linearaliphatic, respectively olefinic, hydrocarbon radical. More preferablyR₁ is a bivalent linear aliphatic hydrocarbon radical. Such a bivalentaliphatic group is sometimes also referred to as an “alkylene” group.

R₁ may or may not include one or more heteroatoms, such as oxygen (O),sulphur (S) and combinations thereof, within the backbone carbon chain.If a heteroatom is present in the backbone carbon chain, such heteroatomis preferably oxygen.

Preferably R₁ comprises a straight backbone carbon chain with nosubstituents.

Such linear C2-C12 diol monomer unit is herein sometimes also referredto as “linear C2-C12 diol-derived monomer unit” or simply as “linearC2-C12 diol unit”.

As mentioned above, it is possible for the polyester copolymer tocontain only one distinct type of linear C2-C12 diol monomer unit, butit is also possible for the polyester copolymer to contain a mixture oftwo or more distinct types of linear C2-C12 diol monomer units.

As explained above, by a C2-C12 diol monomer unit is understood a diolmonomer unit having in the range from equal to or more than 2 to equalto or less than 12 carbon atoms. As example of a linear C2-C12 diolmonomer unit, the polyester copolymer can for example also comprise alinear C3-C12 diol monomer unit (that is, a linear diol monomer unithaving in the range from equal to or more than 3 to equal to or lessthan 12 carbon atoms), a linear C2-C10 diol monomer unit (that is, alinear diol monomer unit having in the range from equal to or more than2 to equal to or less than 10 carbon atoms) or a linear C3-C10 diolmonomer unit (that is, a linear diol monomer unit having in the rangefrom equal to or more than 3 to equal to or less than 10 carbon atoms).

The linear C2-C12 diol monomer unit is suitably derived from a linearC2-C12 diol. By a linear diol is herein preferably understood anon-cyclic essentially straight-chain diol.

The linear C2-C12 diol monomer unit can be a linear diol monomer unitcontaining an even or odd number of carbon atoms, for example 2, 3, 4,5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms. Preferably the linear C2-C12diol monomer unit is a linear diol monomer unit having a chemicalstructure according to formula (IV), wherein R₁ is an alkylene groupwith structure —[CH₂]_(n)—, wherein n suitably represents a number of—[CH₂]— units and wherein n is a number in the range from 1 to 10. Thenumber n can be an even or odd number and suitably n can be 1, 2, 3, 4,5, 6, 7, 8, 9 or 10. Examples of suitable linear C2-C12 diol monomerunits include monomer units derived from ethyleneglycol(ethane-1,2-diol), propane-1,3-diol, propene-1,3-diol, butane-1,4-diol,butene-1,4-diol, pentane-1,5-diol, pentene-1,5-diol, hexane-1,6-diol,hexene-1,6-diol, hexadiene-1,6-diol, heptane-1,7-diol, heptene-1,7-diol,octane-1,8-diol, octene-1,8-diol, octadiene-1,8-diol, nonane-1,9-diol,nonene-1,9-diol, decane-1,10-diol, decene-1,10-diol, undecane-1,11-diol,undecene-1,11-diol, dodecane-1,12-diol, dodecene-1,12-diol,diethyleneglycol (DEG; 2,2′-Oxydi(ethan-1-ol)), triethyleneglycol (TEG;2,2′-[Ethane-1,2-diylbis(oxy)]di(ethan-1-ol)), dipropylene glycol(4-Oxa-2,6-heptandiol) and mixtures of two or more thereof.

More preferably the linear C2-C12 diol monomer unit comprises abutane-1,4-diol monomer unit (also referred to as a bivalent butylene ortetramethylene group), a hexane-1,6-diol monomer unit (also referred toas a bivalent hexylene or hexamethylene group), a diethyleneglycolmonomer unit, a triethyleneglycol monomer unit, or a mixture of one ormore of these. Most preferably the polyester copolymer contains only onetype of linear C2-C12 diol monomer unit, and most preferably such linearC2-C12 diol monomer unit is a butane-1,4-diol monomer unit, ahexane-1,6-diol monomer unit, a diethyleneglycol monomer unit or atriethyleneglycol monomer unit.

The linear C2-C12 diol monomer unit is preferably obtained and/orderived from a sustainable source. For example the C2-C12 diol monomerunit may be obtained and/or derived from a sustainable biomass material.For example, WO 2009/065778 describes the production of succinic acid ina eukaryotic cell, which can for example be subsequently partlyhydrogenated to prepare butane-1,4-diol.

The polyester copolymer preferably contains in the range from equal toor more than 0.1 mole % to equal to or less than 25.0 mole %, based onthe total amount of moles of monomer units within the polyestercopolymer, of one or more linear C2-C12 diol monomer units. Morepreferably, the polyester copolymer contains in the range from equal toor more than 1 mole %, more preferably equal to or more than 3 mole %and most preferably equal to or more than 5 mole % to equal to or lessthan 25 mole %, more preferably equal to or less than 25.0 mole %, basedon the total amount of moles of monomer units within the polyestercopolymer, of one or more linear C2-C12 diol monomer units. As indicatedabove, the percentages here are unit percentages, also referred tosometimes as mole unit percentages. That is, the percentages arecalculated in “moles” of monomer units.

As indicated above, the amounts of bicyclic diol monomer unit and thetype and amount of linear C2-C12 diol monomer units can conveniently betargeted towards a desired Tg value. For some applications the polyestercopolymer is preferably a polyester copolymer containing in the rangefrom equal to or more than 5.0 mole %, more preferably equal to or morethan 15.0 mole %, to equal to or less than 25.0 mole %, based on thetotal amount of moles of monomer units within the polyester copolymer,of linear C2-C12 diol monomer units. For other applications thepolyester copolymer is preferably a polyester copolymer containing inthe range from equal to or more than 0.1 mole %, more preferably equalto or more than 5.0 mole %, to equal to or less than 15.0 mole %, basedon the total amount of moles of monomer units within the polyestercopolymer, of linear C2-C12 diol monomer units.

In addition to the one or more bicyclic diol monomer units, oxalatemonomer unit and one or more linear C2-C12 diol monomer units, thepolyester copolymer may optionally contain one or more additionalmonomer units (as listed under (d)). Such additional monomer units aresometimes also referred to as “additional units”.

For example the polyester copolymer may suitably contain one or morecrosslinking monomer units. Such optional crosslinking monomer units maybe advantageous for increasing the polymer melt viscosity of thepolyester copolymer. A higher polymer melt viscosity may in some casesbe advantageous, for example when the polymer is melt extruded and/orfor the preparation of films, fibers, injection moulded parts and/orpackaging materials such as containers. Examples of such optionalcrosslinking monomer units include monomer units derived fromcrosslinking compounds having three or more carboxylic acid functions,hydroxyl functions or a mixture thereof, such as for example1,2,4-benzenetricarboxylic acid, trimethyl-1,2,4-benzenetricarboxylate,1,2,4-benzenetricarboxylic anhydride, 1,3,5-benzenetricarboxylic acid,1,2,4,5-benzenetetracarboxylic acid, 1,2,4,5-benzenetetracarboxylicdianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride,1,4,5,8-naphthalenetetracarboxylic dianhydride, citric acid,tetrahydrofuran-2,3,4,5-tetracarboxylic acid,1,3,5-cyclohexanetricarboxylic acid, pentaerythritol,2-(hydroxymethyl)-1,3-propanediol, 2,2-bis(hydroxymethyl)propionic acid.

If one or more optional crosslinking monomer units are present, thepolyester copolymer preferably contains in the range from equal to ormore than 0.1 mole % to equal to or less than 5.0 mole % of acrosslinking monomer unit, based on the total amount of moles of monomerunits within the polyester copolymer. More preferably the polyestercopolymer contains in the range from equal to or more than 0.1 mole % toequal to or less than 2.0 mole % of crosslinking monomer unit, based onthe total amount of moles of monomer units within the polyestercopolymer. In a preferred embodiment essentially no crosslinking monomerunits are present.

The additional monomer units can also comprise one or more hydroxy acidmonomer units, derived from one or more hydroxy acid compounds.

For example, the polyester copolymer may contain hydroxy acid monomerunits derived from hydroxy acid compounds such as for example glycolicacid, lactic acid, hydroxybutyric acid, hydroxycaproic acid,hydroxyvaleric acid, 7-hydroxyheptanoic acid, 8-hydroxyoctanoic acid,9-hydroxynonanoic acid, hydroxymethylfurancarboxylic acid orhydroxybenzoic acid units or a mixture of these hydroxy acids. Ifpresent, the percentage of hydroxy acid monomer units, based on thetotal amount of moles of monomer units of the polyester copolymer, ispreferably equal to or less than 5.0 mole %, more preferably equal to orless than 1.0 mole %. Most preferably the polyester copolymer containsessentially no hydroxy acid monomer units. That is, the polyestercopolymer according to the invention can be devoid of hydroxy acidmonomer unit.

As indicated above, the additional monomer units may optionally alsocomprise one or more dicarboxylate monomer units other than the oxalatemonomer unit. If present, the additional monomer units can for examplealso comprise one or more linear C3-C12 dicarboxylate monomer units,such as for example a succinate monomer unit, adipate monomer unit,suberate monomer unit, sebacate monomer unit, furan dicarboxylatemonomer unit, terephthalate monomer unit or a mixture of one or more ofthese.

If present, the polyester copolymer preferably contains in the rangefrom equal to or more than 0.0 mole % to equal to or less than 5.0 mole%, more preferably equal to or less than 1.0 mole %, based on the totalamount of moles of monomer units within the polyester copolymer, of oneor more linear C3-C12 dicarboxylate monomer units. Most preferably thepolyester copolymer contains essentially no such linear C3-C12dicarboxylate monomer units. That is, the polyester copolymer accordingto the invention can be devoid of any linear C3-C12 dicarboxylatemonomer units. Even more preferably the polyester copolymer is devoid ofany dicarboxylate monomer units other than the oxalate monomer units.

The additional monomer units may optionally also comprise one or morediol monomer units other than the bicyclic diol monomer unit or linearC2-C12 diol monomer unit. If present, the additional monomer units canfor example also comprise one or more other diol monomer units, such asfor example a 1,4-cyclohexanedimethanol monomer unit and/or acyclobutanediol monomer unit. If present, the polyester copolymerpreferably contains in the range from equal to or more than 0.0 mole %to equal to or less than 5.0 mole %, more preferably equal to or lessthan 1.0 mole %, based on the total amount of moles of monomer unitswithin the polyester copolymer, of one or more other diol monomer units.Most preferably the polyester copolymer contains essentially no suchother diol monomer units. That is, the polyester copolymer according tothe invention is preferably devoid of any diol monomer units other thanthe bicyclic diol monomer units (as listed under (a)) and/or the linearC2-C12 diol monomer units (as listed under (b)).

The additional monomer units can also comprise one or more chainextending monomer units. By a “chain extending” monomer unit is hereinunderstood a monomer unit comprising functional groups other thanhydroxyl, carboxylic acid and/or ester, which functional groups arecapable of reacting with these same functional groups in another type ofpolymer. Examples include for example functional groups such asisocyanate and/or imide functions. The polyester copolymer may or maynot include such chain extending monomer units. If present, thepolyester copolymer preferably contains in the range from equal to ormore than 0.0 mole % to equal to or less than 5.0 mole %, morepreferably equal to or less than 1.0 mole %, based on the total amountof moles of monomer units within the polyester copolymer, of one or morechain extending monomer units. Possibly the polyester copolymer containsessentially no such chain extending monomer units.

Preferably the total weight percentage of any additional monomers unitsis equal to or less than 1 weight percent (wt %), more preferably equalto or less than 0.1 wt % and even more preferably equal to or less than0.01 wt % of the total weight of the polyester copolymer. Mostpreferably polyester copolymer contains essentially no additionalmonomers units.

That is, preferably the polyester copolymer is a polyester copolymer,having a number average molecular weight of equal to or more than 5000grams/mole and having a glass transition temperature of less than 160°C., preferably equal to or less than 140° C., essentially consisting ofor solely consisting of:

(a) in the range from equal to or more than 25.0 mole % to equal to orless than 49.9 mole %, based on the total amount of moles of monomerunits within the polyester copolymer, of one or more bicyclic diolmonomer units, wherein such one or more bicyclic diol monomer unitsis/are derived from one or more bicyclic diols chosen from the groupconsisting of isosorbide, isoidide, isomannide,2,3:4,5-di-O-methylene-galactitol and 2,4:3,5-di-O-methylene-D-mannitol;(b) in the range from equal to or more than 45.0 mole % to equal to orless than 50.0 mole %, based on the total amount of moles of monomerunits within the polyester copolymer, of an oxalate monomer unit; and(c) in the range from equal to or more than 0.1 mole % to equal to orless than 25.0 mole %, based on the total amount of moles of monomerunits within the polyester copolymer, of one or more linear C2-C12 diolmonomer units, wherein such one or more linear C2-C12 diol monomer unitsis/are derived from one or more linear C2-C12 diols.

Suitably the total amount of moles of monomer units in the polyestercopolymer adds up to essentially 100.0 mole %.

Preferably the ratio of moles of bicyclic diol monomer units (as listedunder (a)), preferably moles of 1,4:3,6-dianhydrohexitols monomer units,to moles of linear C2-C12 diol monomer unit (as listed under (c))—i.e.the molar ratio of bicyclic diol monomer unit:linear C2-C12 diol monomerunit—is equal to or more than 1:1, more preferably equal to or more than1.5:1.

The amounts of bicyclic diol monomer unit, preferably1,4:3,6-dianhydrohexitols monomer units, and linear C2-C12 diol monomerunits can advantageously be targeted towards a desired Tg. For someapplications (for example, where a higher Tg may be desired) it can beadvantageous for the polyester copolymer to be a polyester copolymerwherein the molar ratio of bicyclic diol monomer units (respectively1,4:3,6-dianhydrohexitols monomer units) to linear C2-C12 diol monomerunits is equal to or more than 2:1 and equal to or less than 20:1 orequal to or less than 10:1. For other applications (for example, where alower Tg may be desired) it can be advantageous for the polyestercopolymer to be a polyester copolymer wherein the molar ratio ofbicyclic diol monomer units (respectively 1,4:3,6-dianhydrohexitolsmonomer units) to linear C2-C12 diol monomer units is equal to or morethan 1:1 or equal to or more than 1.5:1 and equal to or less than 2:1.

The amounts of each of the different monomer units in the polyestercopolymer can be determined by proton nuclear magnetic resonance (¹HNMR). One skilled in the art would easily find the conditions ofanalysis to determine the amount of each of the different monomer unitsin the polyester copolymer.

The polyester copolymer(s) according to the invention can be a randomcopolymer or a block copolymer.

The number average molecular weight (Mn) of the polyester copolymer(s)may vary widely and may depend for example on the catalyst, reactiontime and reaction temperature. The polyester copolymer(s) according tothe invention preferably has/have a number average molecular weight ofequal to or more than 9000 grams/mole, more preferably of equal to ormore than 12000 grams/mole, still more preferably equal to or more than15000 grams/mole, even more preferably of equal to or more than 17000grams/mole, and still even more preferably of equal to or more than20000 grams/mole and preferably of equal to or less than 150000grams/mole, even more preferably of equal to or less than 100000grams/mole. The weight average molecular weight and number averagemolecular weight can conveniently be determined through gel permeationchromatography (GPC) at 25° C. using polystyrene standards and using amixture of chloroform and 2-chlorophenol in a volumetric ratio of 6:4(chloroform:2-chlorophenol) as eluent. All molecular weights herein aredetermined as described under the analytical methods section of theexamples.

Suitably the polyester copolymer according to the present invention mayhave a polydispersity index (that is, the ratio of weight averagemolecular weight (Mw) to number average molecular weight (Mn), i.e.Mw/Mn) in the range from equal to or more than 1.6 to equal to or lessthan 2.6.

The polyester copolymer(s) according to the invention preferablyhas/have a glass transition temperature (Tg) equal to or more than minus60° C. (−60° C.), more preferably equal to or more than minus 20° C.(−20° C.), still more preferably equal to or more than 20° C., and/orless than 160° C., preferably equal to or less than 150° C., still morepreferably equal to or less than 140° C., yet still more preferablyequal to or less than 135° C. and possibly equal to or less than 130° C.

For some applications, such as for example glue, car bumpers, outdoorfurniture or some films, it may be advantageous for the polyestercopolymer to be a polyester copolymer having a glass transitiontemperature in the range from equal to or more than minus 60° C. (−60°C.), preferably equal to or more than minus 20° C. (−20° C.), possiblyeven equal to or more than 20° C., to equal to or less than 100° C.,more preferably equal to or less than 80° C. For other applications,such as for example injection molded parts or (other) heat-resistancerequiring applications, it may be advantageous for the polyestercopolymer to be a polyester copolymer having a glass transitiontemperature in the range from equal to or more than 60° C., morepreferably equal to or more than 80° C., still more preferably equal toor more than 100° C., to less than 160° C., more preferably equal to orless than 140° C., still more preferably equal to or less than 130° C.or yet still more preferably equal to or less than 120° C. For stillother applications, such as for example the replacement of PET bottles,it may be advantageous for the polyester copolymer to be a polyestercopolymer having a glass transition temperature in the range from equalto or more than 60° C. to equal to or less than 120° C. or equal to orless than 100° C. Advantageously the glass transition temperature (Tg)of the polyester copolymer according to the invention does not need tobe fixed and can be targeted, for example by varying the amounts of thedifferent type of monomer units (a), (b), (c) and optionally (d), to aspecific desired Tg, as described in detail above. Advantageously, theglass transition temperature (Tg) may, if so desired, even be variedwhilst still a commercially advantageous high number average molecularweight (Mn) is obtained.

The glass transition temperature of the polyester copolymer canconveniently be measured by conventional methods, in particular by usingdifferential scanning calorimetry (DSC) with a heating rate of 10°C./minute in a nitrogen atmosphere. All glass transition temperaturesherein are determined as described under the analytical methods sectionof the examples.

Preferably the polyester copolymer as a whole is (via its monomers)partially or completely obtained and/or derived from one or moresustainable sources, preferably from sustainable biomass material and/orcarbon monoxide and/or carbon dioxide. More preferably the polyestercopolymer is completely obtained and/or derived from such one or moresustainable sources. Preferably the polyester copolymer is obtainedand/or derived, in part or in whole, from sources other than coal, gasor petroleum.

The polyester copolymer can advantageously be produced by the processfor the production of a polyester copolymer as described herein aboveunder the summary of the invention. More preferably the polyestercopolymer can be produced by a process for the production of a polyestercopolymer preferably comprising polymerizing the following monomers:

(i) in the range from equal to or more than 25.0 mole percent (mole %)to equal to or less than 49.9 mole %, based on the total amount of molesof monomers, of one or more bicyclic diols chosen from the groupconsisting of isosorbide, isoidide, isomannide,2,3:4,5-di-O-methylene-galactitol and 2,4:3,5-di-O-methylene-D-mannitol;(ii) in the range from equal to or more than 45.0 mole % to equal to orless than 50.0 mole %, based on the total amount of moles of monomers,of one or more oxalic diesters having a chemical structure according toformula (VI):

wherein R₂ and R₃ each independently are a C3-C20 alkyl group, a C2-C20alkenyl group, a C4-C20 cycloalkyl group, a C4-C20 aryl group or aC5-C20 alkylarylgroup;(iii) in the range from equal to or more than 0.1 mole % to equal to orless than 25.0 mole %, based on the total amount of moles of monomers,of one or more linear C2-C12 diols; and(iv) optionally equal to or more than 0.0 mole % to equal to or lessthan 5.0 mole %, based on the total amount of moles of monomers, of oneor more additional monomers.

The process for the production of a polyester copolymer can comprisemelt polymerization and/or solid state polymerization.

For example, the process can comprise melt mixing of the monomers in thepresence of a metal-containing catalyst (also referred to herein as meltpolymerization).

The polyester copolymer according to the invention can for example beproduced by a process for the production of a polyester copolymercomprising melt mixing of the monomers, at a temperature in the rangefrom equal to or more than 175° C., more preferably equal to or morethan 180° C., and even more preferably equal to or more than 190° C. toequal to or less than 300° C., more preferably equal to or less than275° C., and even more preferably equal to or less than 250° C. in thepresence of a metal-containing catalyst. The melt mixing can suitably becarried out in a reactor. Hence, the melt mixing may suitably bepreceded by an introduction stage, wherein the monomers are introducedinto a reactor, and succeeded by a recovery stage, wherein the polyestercopolymer is recovered from a reactor.

The process for the production of a polyester copolymer can alsocomprise a combination of melt polymerization and solid statepolymerization, wherein the polyester copolymer product of a meltpolymerization step is followed by a solid state polymerization step.

Preferences for the one or more bicyclic diols (as listed under (i)) areas mentioned in the text relating to the bicyclic diol monomer unitabove. Preferably the one or more bicyclic diols is/are one or more1,4:3,6-dianhydrohexitols. For example the bicyclic diol may be a1,4:3,6-dianhydrohexitol having a chemical structure according toformula (V)

As mentioned above, examples of suitable 1,4:3,6-dianhydrohexitolsinclude isosorbide (1,4:3,6-dianhydro-D-glucidol), isoidide(1,4:3,6-dianhydro-L-iditol), isomannide (1,4:3,6-dianhydro-D-mannitol)and mixtures thereof. These may have structures according to formulae(IA), (IB) and (IC) as described above. It is possible to include amixture of two or more isomers of 1,4:3,6-dianhydrohexitols, for examplea mixture of isosorbide and/or isomannide and/or isoidide. Preferably,however, only one isomer of 1,4:3,6-dianhydrohexitol is used. Morepreferably the 1,4:3,6-dianhydrohexitol is/are isosorbide and/orisoidide. Still more preferably the 1,4:3,6-dianhydrohexitol is anisosorbide.

The one or more 1,4:3,6-dianhydrohexitols are preferably obtained and/orderived from a sustainable source, preferably from a sustainable biomassmaterial. Further preferences are as described in the text relating tothe 1,4:3,6-dianhydrohexitol monomer unit.

In the process according to the invention preferably in the range fromequal to or more than 25 mole %, more preferably equal to or more than25.0 mole %, to equal to or less than 49.9 mole percent, of bicyclicdiol, respectively 1,4:3,6-dianhydrohexitol, based on the total amountof moles of monomers, are used. Further preferences are explained above.For some applications a range from equal to or more than 25.0 mole % toequal to or less than 45.0 mole %, more preferably to equal to or lessthan 35.0 mole % of bicyclic diol, preferably 1,4:3,6-dianhydrohexitol,based on the total amount of moles of monomers, is preferred. For otherapplications a range from equal to or more than 35.0 mole % to equal toor less than 49.9 mole %, more preferably to equal to or less than 45.0mole % of bicyclic diol, preferably 1,4:3,6-dianhydrohexitol, based onthe total amount of moles of monomers, is preferred.

The oxalic diester (as listed under (ii)) may suitably have a chemicalstructure according to formula (VI):

wherein R₂ and R₃, each independently, are a C3-C20 alkyl group, aC2-C20 alkenyl group, a C4-C20 cycloalkyl group, a C4-C20 aryl group ora C5-C20 alkylarylgroup.

Preferably R₂ and R₃, each independently, are a C2-C20 alkenyl group.

Preferably R₂ and R₃, each independently, are a group having a chemicalstructure according to formula (X):

wherein R₄, R₅ and R₆, each independently, represent hydrogen or a C1-C6alkyl group, orwherein R₄ and R₅ together or R₄ and R₆ together form a C4-C20cycloalkyl group, a C4-C20 aryl group or a C5-C20 alkylarylgroup.

For example, R₄, R₅ and R₆, each independently, can represent hydrogenor a C1-C4 alkyl group. It is also possible for R₄ and R₅ together or R₄and R₆ together to form a C5-C10 cycloalkyl group, a C5-C10 aryl groupor a C5-C10 alkylarylgroup.

More preferably, at least one of R₂ and R₃, and preferably both of R₂and R₃, are chosen from the group consisting of n-propyl, iso-propyl,n-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, tert-butyl,phenyl, methylphenyl, ethylphenyl, vinyl (ethenyl), allyl (2-propenyl)and/or 1-propenyl. Most preferably at least one of R₂ and R₃, andpreferably both of R₂ and R₃, are phenyl, methylphenyl, allyl and/orvinyl.

Preferably the oxalic diester is a diester of oxalic acid and analkanol, wherein the alkanol has a pKa of equal to or less than 20.0,more preferably equal to or less than 16.0, even more preferably equalto or less than 15.0 and still more preferably equal to or less than12.0, such as for example phenol (pKa 10.0), 2-methyl phenol (pKa 10.3),3-methyl phenol (pKa 10.1), 4-methyl phenol (pKa 10.3), vinyl alcohol(ethenol, pKa 10.5) and/or allyl alcohol (Prop-2-en-1-ol). As apractical minimum the pKa is preferably equal to or more than 7.0.

Most preferably the oxalic diester is di(phenyl)oxalate,di(methylphenyl)oxalate, di(allyl) oxalate, di(vinyl) oxalate,monomethylmonophenyloxalate or a mixture of one or more thereof.

It is possible to include a mixture of two or more oxalic diesters forexample a mixture of di(phenyl)oxalate, di(methylphenyl)oxalate,di(allyl) oxalate and/or di(vinyl) oxalate. Preferably, however, onlyone oxalic diester is used, most preferably only di(phenyl)oxalate, onlydi(methylphenyl)oxalate, only di(allyl)oxalate or only di(vinyl) oxalateis used.

The one or more oxalic diesters are preferably obtained and/or derivedfrom a sustainable source, preferably from a sustainable biomassmaterial. Preferences are as described in the text relating to theoxalate monomer unit above.

It is especially preferred for the oxalic diester monomer to be a oxalicdiester obtained and/or derived from carbon monoxide and/orcarbondioxide (CO₂), for example with the help of an electrochemicalconversion. For example WO 2014/100828 and WO2015184388 describe theelectrochemical conversion of CO₂ to oxalate and oxalic acid and theircontents are herein incorporated by reference. The therein mentionedoxalate and oxalic acid can be converted to an oxalic diester byconventional means.

In the process according to the invention preferably in the range fromequal to or more than 45.0 mole % to equal to or less than 50.0 mole %of oxalic diester, based on the total amount of moles of monomers, morepreferably in the range from equal to or more than 49.0 mole % to equalto or less than 50.0 mole % of oxalic diester, based on the total amountof moles of monomers, are used.

As indicated above, in addition to the one or more oxalic diesters, oneor more other diesters may be used in a low amount, for example in anamount from equal to or more than 0.1 mole % to equal to or less than5.0 mole %, based on the total amount of moles of monomers. Examplesinclude for example diesters from C3-C12 aliphatic diacids, such assuccinic acid, adipic acid, suberic acid, furan dicarboxylic acid and/orterephthalic acid. Preferably, however, the process is carried out inthe essential absence of any other diesters, that is, it is carried outin the essential absence of any diesters other than the one or moreoxalic diesters.

Preferences for the one or more linear C2-C12 diols (as listed under(iii)) are as for the linear C2-C12 diol monomer unit above. Asexplained above, by a linear C2-C12 diol is herein understood a lineardiol having in the range from equal to or more than 2 to equal to orless than 12 carbon atoms. As examples of a linear C2-C12 diol, forexample also a linear C3-C12 diol (that is, a linear diol having in therange from equal to or more than 3 to equal to or less than 12 carbonatoms), a linear C2-C10 diol (that is, a linear diol having in the rangefrom equal to or more than 2 to equal to or less than 10 carbon atoms)or a linear C3-C10 diol (that is, a linear diol having from equal to ormore than 3 to equal to or less than 10 carbon atoms), can be used.

Such one or more linear C2-C12 diols may have a chemical structureaccording to formula (VII):HO—R₁—OH  (VII)wherein R₁ is a linear organic group, as described above for formula(IV).

Preferences for R₁ are as described above for formula (IV). Preferably,the linear C2-C12 diol is a linear diol having a chemical structureaccording to formula (VII), wherein R₁ is an alkylene group withstructure —[CH₂]_(n)—, wherein n suitably represents the number of—[CH₂]— units and wherein n is a number in the range from 1 to 10. Thenumber n can be an even or odd number and suitably n can be 1, 2, 3, 4,5, 6, 7, 8, 9 or 10.

Further preferences are as described above in the text for the linearC2-C12 diol monomer unit. Most preferred are butane-1,4-diol,hexane-1,6-diol, diethyleneglycol, triethyleneglycol or a mixture of oneor more of these.

As mentioned above, it is preferred to use only one distinct linearC2-C12 diol in the process according to the invention, but it is alsopossible to use a mixture of two or more distinct linear C2-C12 diols inthe process.

The one or more linear C2-C12 diols are preferably obtained and/orderived from a sustainable source, preferably from a sustainable biomassmaterial. Preferences are as explained for the linear C2-C12 diolmonomer units described above.

In the process according to the invention preferably in the range fromequal to or more than 0.1 mole % to equal to or less than 25 mole %,more preferably equal to or less than 25.0 mole % of one or more linearC2-C12 diols, based on the total amount of moles of monomers, are used.More preferably in the range from equal to or more than 1 mole %, stillmore preferably equal to or more than 3 mole %, and even more preferablyequal to or more than 5 mole %, or equal to or more than 10 mole % toequal to or less than 25 mole %, more preferably equal to or less than25.0 mole % of one or more linear C2-C12 diols, based on the totalamount of moles of monomers, are used. It is, however, also possible touse in the range from equal to or more than 1.0 mole % to equal to orless than 15.0 mole % of one or more linear C2-C12 diols, based on thetotal amount of moles of monomers.

In addition to the one or more bicyclic diols, one or more oxalicdiesters and one or more linear C2-C12 diols, optionally one or moreadditional monomers can be used in the process of the invention.

For example, as additional monomer, one or more crosslinking compounds,precursors for the above mentioned crosslinking monomer units, canoptionally be added. Preferences for the type of such crosslinkingcompounds are as described above. If one or more optional crosslinkingcompounds are present, they are preferably present in the range fromequal to or more than 0.1 mole % to equal to or less than 5.0 mole % ofa crosslinking compound, based on the total amount of moles of monomers,more preferably in the range from equal to or more than 0.1 mole % toequal to or less than 2.0 mole % of crosslinking compound, based on thetotal amount of moles of monomers. In a preferred embodiment essentiallyno crosslinking compounds are present. That is, preferably the processaccording to the invention is carried out in the essential absence ofsuch a crosslinking compound.

The additional monomer(s) can also comprise one or more hydroxy acidcompounds. Preferences for the type of such hydroxy acid compounds areas described above. If present, the amount of hydroxy acid compounds,based on the total amount of monomers, is preferably equal to or lessthan 5.0 mole %, more preferably equal to or less than 1.0 mole %. Morepreferably essentially no hydroxy acid compounds are present.

The additional monomer(s) can also comprise one or more linear C3-C12diacids, acidesters and/or diesters. Examples of suitable linear C3-C12diacids, acidesters and/or diesters include linear C3-C12 diacids,acidesters and/or diesters chosen from the group consisting of succinicacid, adipic acid, di(phenyl)succinate, di(phenyl)adipate,di(methylphenyl)succinate, di(methylphenyl)adipate, di(vinyl)succinateand di(vinyl)adipate. If present, the amount of one or more linearC3-C12 diacids, acidesters and/or diesters, based on the total amount ofmonomers, is preferably in the range from equal to or more than 0.0 mole% to equal to or less than 5.0 mole %, more preferably equal to or lessthan 1.0 mole %. More preferably, essentially no linear C3-C12 diacids,acidesters and/or diesters are present. Even more preferably essentiallyno diesters other than the oxalic diester are present.

The process according to the invention may be carried out in thepresence of one or more additives, such as stabilizers, for examplelight stabilizers, UV stabilizers and heat stabilizers, fluidifyingagents, flame retardants and antistatic. Other additives include primaryand/or secondary antioxidants. A primary antioxidant can for example bea sterically hindered phenol, such as the compounds Hostanox® 0 3,Hostanox® 0 10, Hostanox® 0 16, Ultranox® 210, Ultranox®276, Dovernox®10, Dovernox® 76, Dovernox® 3114, Irganox® 1010 or Irganox® 1076. Asecondary antioxidant can for example be a trivalentphosphorous-comprising compounds, such as Ultranox® 626, Doverphos®S-9228 or Sandostab® P-EPQ.

The process according to the invention may comprise several stages.Suitably the process according to the invention may comprise atransesterification stage and a polycondensation stage, wherein thetransesterification stage is carried out prior to the polycondensationstage. The transesterification stage may suitably be preceded by anintroduction stage, wherein the above monomers, such as the bicyclicdiol monomer(s), oxalic diester monomer(s), linear C2-C12 diolmonomer(s) and optional additional monomer(s), are introduced into areactor. The polycondensation stage may suitably be succeeded by arecovery stage, wherein the polyester copolymer is recovered from areactor.

The process according to the invention can be carried out in abatch-wise, semi-batchwise or continuous mode. The transesterificationstage and the polycondensation stage may conveniently be carried out inone and the same reactor, but may also be carried out in two separatereactors, for example where the transesterification stage is carried outin a first transesterification reactor and the polycondensation stage iscarried out in a second polycondensation reactor.

The process according to the invention may thus suitably comprise thefollowing stages:

an introduction stage, wherein the bicyclic diol monomer(s), oxalicdiester monomer(s), linear C2-C12 diol monomer(s) and optionaladditional monomer(s), are introduced into a reactor;

a transesterification stage, wherein the monomers are reacted in atransesterification reaction, and optionally a pre-polycondensationreaction, to thereby produce oligomers;

a polycondensation stage, wherein the oligomers are reacted further in apolycondensation reaction to thereby produce the polyester copolymer;and

a recovery stage, wherein the polyester copolymer is recovered from thereactor.

The polycondensation stage may suitably be carried out at a temperatureequal to or higher than the temperature at which the transesterificationstage is carried out. The transesterification stage may for example becarried out at a temperature in the range from equal to or more than165° C., more preferably equal to or more than 180° C., and even morepreferably equal to or more than 190° C., to equal to or less than 200°C. The polycondensation stage may suitably succeed thetransesterification stage and the polycondensation stage can for examplebe carried out at a temperature in the range from equal to or more than195° C., more preferably equal to or more than 200° C., to equal to orless than 275° C., more preferably equal to or less than 255° C. andmost preferably equal to or less than 235° C.

Any transesterification stage is preferably carried out over a reactiontime in the range from equal to or more than 0.5 hour, more preferablyequal to or more than 1.0 hour, to equal to or less than 6.0 hour, morepreferably equal to or less than 4.0 hour. During a transesterificationstage, the temperature may be stepwise or gradually increased.

Any polycondensation stage is preferably carried out over a reactiontime in the range from equal to or more than 0.5 hour, more preferablyequal to or more than 1.0 hour, to equal to or less than 8.0 hours, morepreferably equal to or less than 6.0 hours. During a polycondensationstage, the temperature may be stepwise or gradually increased.

In any introduction stage the monomers can be introduced into thereactor simultaneously, for example in the form of a feed mixture, or inseparate parts. The monomers can be introduced into the reactor in amolten phase or they can be molten and mixed after introduction into thereactor.

The polycondensation stage may be succeeded by a recovery stage, whereinthe polyester copolymer as described above is recovered from thereactor. The polyester can for example be recovered by extracting itfrom the reactor in the form of a string of molten polymer. This stringcan be converted into granules using conventional granulationtechniques.

The transesterification stage and/or polycondensation stage arepreferably carried out under an inert gas atmosphere.

More preferably the transesterification stage and/or polycondensationstage are carried out at a reduced pressure. The transesterificationstage, and/or any optional pre-polymerization reaction, may for examplebe carried out at a pressure in the range from equal to or more than10.0 mbar (10.0 millibar, corresponding to 1.00 KiloPascal), morepreferably equal to or more than 100 mbar (corresponding to 10.0KiloPascal), to equal to or less than 1.00 bar (corresponding to 100KiloPascal), more preferably equal to or less than 400 mbar(corresponding to 40.0 KiloPascal). The polycondensation stage may forexample be carried out at a pressure in the range from equal to or morethan 0.01 mbar (corresponding to 1 Pascal), more preferably equal to ormore than 0.1 mbar (corresponding to 10 Pascal) to equal to or less than10.0 mbar (corresponding to 1.0 KiloPascal), more preferably equal to orless than 5.0 mbar (corresponding to 500 Pascal).

The process according to the invention is suitably carried out in thepresence of a metal-containing catalyst. Such metal-containing catalystmay for example comprise derivatives of tin (Sn), titanium (Ti),zirconium (Zr), germanium (Ge), antimony (Sb), bismuth (Bi), hafnium(Hf), magnesium (Mg), cerium (Ce), zinc (Zn), cobalt (Co), iron (Fe),manganese (Mn), calcium (Ca), strontium (Sr), sodium (Na), lead (Pb),potassium (K), aluminium (Al), and/or lithium (Li). Examples of suitablemetal-containing catalysts include salts of Li, Ca, Mg, Mn, Zn, Pb, Sb,Sn, Ge, and Ti, such as acetate salts and oxides, including glycoladducts, and Ti alkoxides. Examples of such compounds can, for example,be those given in US2011282020A1 in sections [0026] to [0029], and onpage 5 of WO 2013/062408 A1. Preferably the metal-containing catalyst isa tin-containing catalyst, for example a tin(IV)- or tin(II)-containingcatalyst. More preferably the metal-containing catalyst is analkyltin(IV) salt and/or alkyltin(II) salt. Examples includealkyltin(IV) salts, alkyltin(II) salts, dialkyltin(IV) salts,dialkyltin(II) salts, trialkyltin(IV) salts, trialkyltin(II) salts or amixture of one or more of these. These tin(IV) and/or tin(II) catalystsmay be used with alternative or additional metal-containing catalysts.Examples of alternative or additional metal-containing catalysts thatmay be used include one or more of titanium(IV) alkoxides ortitanium(IV) chelates, zirconium(IV) chelates, or zirconium(IV) salts(e.g. alkoxides); hafnium(IV) chelates or hafnium(IV) salts (e.g.alkoxides); yttrium(III) alkoxides or yttrium(III) chelates;lanthanum(III) alkoxides or lanthanum chelates; scandium(III) alkoxidesor chelates; cerium(III) alkoxides or cerium chelates. An exemplarymetal-containing catalyst is n-butyltinhydroxideoxide.

In a preferred process the one or more bicyclic diols is/are firstreacted with the one or more oxalic diesters in the presence of ametal-containing catalyst under polymerization conditions (including forexample a temperature in the range from 150° C. to 210° C.) to produce abicyclic diol-oxalate ester product, whereafter the bicyclicdiol-oxalate ester product is subsequently reacted with the one or morelinear C2-C12 diols in the presence of a metal-containing catalyst underfurther polymerization conditions (including for example a temperaturein the range from 200° C. to 255° C.) to produce the polyestercopolymer. The metal-containing catalyst may suitably be as describedbefore.

For example the process may comprise:

-   -   reacting the one or more bicyclic diols, in the presence of a        metal-containing catalyst under polymerization conditions        (including for example a temperature in the range from 150° C.        to 210° C.), with the one or more oxalic diesters having a        chemical structure according to formula (VI):

wherein R₂ and R₃, each independently, are a C3-C20 alkyl group, aC2-C20 alkenyl group, a C4-C20 cycloalkyl group, a C4-C20 aryl group ora C5-C20 alkylarylgroup, to yield a bicyclic diol-oxalate ester product;and

-   -   subsequently reacting the bicyclic diol-oxalate ester product        with one or more linear C2-C12 diols in the presence of a        metal-containing catalyst under further polymerization        conditions (including for example a temperature in the range        from 200° C. to 255° C.) to produce the polyester copolymer.

Further preferences are as described above.

In an alternative process the one or more bicyclic diols is/are firstreacted with the one or more oxalic diesters in the presence of ametal-containing catalyst under polymerization conditions (including forexample a temperature in the range from 150° C. to 210° C.), suitably ina first reactor, to form a first ester product. In parallel therewith,suitably in a second reactor, the one or more oxalic diesters is/arereacted with the one or more linear C2-C12 diols in the presence of ametal-containing catalyst under polymerization conditions (including forexample a temperature in the range from 150° C. to 210° C.) to form asecond ester product. The metal-containing catalyst may suitably be asdescribed before. In a subsequent step the first ester product and thesecond ester product are combined and subjected to furtherpolymerization and/or transesterification in the presence of ametal-containing catalyst (for example at a temperature in the rangefrom 200° C. to 255° C.) to produce the polyester copolymer.

The process according to the invention can further comprise, after arecovery stage (i.e. wherein the polyester copolymer is recovered fromthe reactor) as described above, a stage of polymerization in the solidstate. That is, the polyester copolymer recovered as described above canbe polymerized further in the solid state, thereby increasing chainlength. Such polymerization in the solid state is also referred to as asolid state polymerization (SSP). Such a solid state polymerizationadvantageously allows one to further increase the number averagemolecular weight of the polyester copolymer. It can furtheradvantageously enhance the mechanical and rheological properties ofpolyester copolymers before injection blow molding or extruding. Thesolid state polymerization preferably comprises heating the polyestercopolymer in the essential or complete absence of oxygen and water, forexample by means of a vacuum or purging with an inert gas.

Advantageously the process according to the invention can thereforecomprise:

a melt polymerization wherein the above described monomers arepolymerized in a melt to produce a polyester copolymer melt product;

an optional pelletisation wherein the polyester copolymer melt productis converted into pellets, and the optional drying of the pellets undervacuum or with the help of inert gas purging;

a solid state polymerization of the polyester copolymer melt product,optionally in the form of pellets, at a temperature above the Tg of thepolyester copolymer melt product and below the melt temperature of thepolyester copolymer melt product.

For the present invention, the solid state polymerization may suitablybe carried out at a temperature in the range from equal to or more than150° C. to equal to or less than 220° C. The solid state polymerizationmay suitably be carried out at ambient pressure (i.e. 1.0 bar atmospherecorresponding to 0.1 MegaPascal) whilst purging with a flow of an inertgas (such as for example nitrogen or argon) or may be carried out at avacuum, for example a pressure equal to or below 100 millibar(corresponding to 0.01 MegaPascal).

The solid state polymerization may suitably be carried out for a periodup to 120 hours, more suitably for a period in the range from equal toor more than 2 hours to equal to or less than 60 hours. The duration ofthe solid state polymerization may be tuned such that a desired finalnumber average molecular weight for the polyester copolymer is reached.

The present invention further provides a polyester copolymer, preferablyobtained or obtainable by a process according to the invention asdescribed above, containing or consisting of the following repeatingunits:

in the range from equal to or more than 45.0 mole % to equal to or lessthan 99.9 mole %, based on the total amount of moles of repeating unitswithin the polyester copolymer, of one or more bicyclic diol-oxalaterepeating units chosen from the group consisting of isosorbide-oxalate,isoidide-oxalate, isomannide-oxalate,2,3:4,5-di-O-methylene-galactitol-oxalate and2,4:3,5-di-O-methylene-D-mannitol-oxalate;

in the range from equal to or more than 0.1 mole % to equal to or lessthan 50.0 mole %, based on the total amount of moles of repeating unitswithin the polyester copolymer, of one or more linear C2-C12diol-oxalate repeating units;

optionally in the range from equal to or more than 0.0 mole % to equalto or less than 5.0 mole %, based on the total amount of moles ofrepeating units within the polyester copolymer, of one or moreadditional repeating units,

wherein the molar ratio of bicyclic diol-oxalate repeating units tolinear C2-C12 diol-oxalate repeating units is equal to or more than 1:1,more preferably equal to or more than 1.5:1.

Such polyester copolymer preferably has a number average molecularweight of equal to or more than 5000 grams/mole and preferably has aglass transition temperature of less than 160° C., more preferably equalto or less than 140° C.

In addition, such polyester copolymer preferably has in the range fromequal to or more than 1 mole %, more preferably equal to or more than 3mole % and still more preferably equal to or more than 5 mole % to equalto or less than 50 mole %, more preferably equal to or less than 50.0mole %, based on the total amount of moles of repeating units within thepolyester copolymer, of the one or more linear C2-C12 diol-oxalaterepeating units.

More preferably, such polyester copolymer is devoid of any additionalrepeating units and preferably such polyester copolymer essentiallyconsists of or completely consists of the one or more bicyclicdiol-oxalate repeating units and the one or more linear C2-C12diol-oxalate repeating units. More preferably the one or more bicyclicdiol-oxalate repeating units are 1,4:3,6-dianhydrohexitol-oxalaterepeating units. Hence more preferably the polyester copolymer is apolyester copolymer essentially consisting of or solely consisting of:

A) in the range from 50.0% to 99.9%, based on the total amount ofrepeating units within the polyester copolymer, of1,4:3,6-dianhydrohexitol-oxalate repeating units having the structuralformula (VIII):

B) in the range from 0.1% to 50.0%, based on the total amount ofrepeating units within the polyester copolymer, of linearC2-C12-diol-oxalate repeating units having the structural formula (IX):having the structural formula (IX):

wherein R₁ suitably represents a linear organic group and preferably isan alkylene group with structure —[CH₂]_(n)—, wherein n suitablyrepresents a number of —[CH₂]— units and wherein n is a number in therange from 2 to 10, with preferences as described for n before; and

wherein the ratio of repeating units with formula (VIII) to repeatingunits with formula (IX), (that is, the repeating units with formula(VIII): repeating units with formula (IX) ratio) is equal to or morethan 1:1, more preferably equal to or more than 1.5:1.

Suitably the percentages of the repeating units are mole percentages,suitably the amounts of repeating units are mole amounts and suitablythe ratio is a molar ratio.

For some applications it can be advantageous for the polyester copolymerto have a ratio of bicyclic diol-oxalate repeating units (respectivelyrepeating units with formula (VIII)) to linear C2-C12 diol-oxalaterepeating units (respectively repeating units with formula (IX)) in therange from equal to or more than 2:1 to equal to or less than 20:1 orequal to or less than 15:1. For other applications it can beadvantageous for the polyester copolymer to have a ratio of repeatingunits with formula (VIII) to repeating units with formula (IX) in therange from equal to or more than 1.5:1 to equal to or less than 3:1,more preferably equal to or less than 2:1.

In line with the indications above, the repeating units may bedistributed along the polyester copolymer in an alternating manner, atrandom or in blocks.

Such polyester copolymer preferably has a number average molecularweight of equal to or more than 5000 grams/mole and preferably has aglass transition temperature of less than 160° C., more preferably equalto or less than 140° C. Further preferences for the above polyestercopolymer (for example for the bicyclic diols and/or linear C2-C12diols, number average molecular weight and glass transition temperature)are as described previously herein for the polyester copolymers.

Examples of polyester copolymers according to the invention includepoly(isosorbide/1,3-propanediol oxalate) (also referred to aspoly(isosorbide/propylene oxalate)), poly(isosorbide/1,4-butanedioloxalate) (also referred to as poly(isosorbide/butylene oxalate)),poly(isosorbide/1,5-pentanediol oxalate) (also referred to aspoly(isosorbide/pentamethylene oxalate)), poly(isosorbide/1,6-hexanedioloxalate) (also referred to as poly(isosorbide/hexamethylene oxalate)),poly(isosorbide/1,7-heptanediol oxalate) (also referred to aspoly(isosorbide/heptamethylene oxalate)), poly(isosorbide/1,8-octanedioloxalate) (also referred to as poly(isosorbide/octamethylene oxalate)),poly(isosorbide/1,9-nonanediol oxalate), poly(isosorbide/1,10-decanedioloxalate), poly(isosorbide/triethylene glycol oxalate) (also referred toas poly(isosorbide/dioxytriethylene oxalate)),poly(isosorbide/diethylene glycol oxalate) (also referred to aspoly(isosorbide/oxydiethylene oxalate)), poly(isoidide/1,3-propanedioloxalate) (also referred to as poly(isoidide/propylene oxalate)),poly(isoidide/1,4-butanediol oxalate) (also referred to aspoly(isoidide/butylene oxalate)), poly(isoidide/1,5-pentanediol oxalate)(also referred to as poly(isoidide/pentamethylene oxalate)),poly(isoidide/1,6-hexanediol oxalate) (also referred to aspoly(isoidide/hexamethylene oxalate)), poly(isoidide/1,7-heptanedioloxalate) (also referred to as poly(isoidide/heptamethylene oxalate)),poly(isoidide/1,8-octanediol oxalate) (also referred to aspoly(isoidide/octamethylene oxalate)), poly(isoidide/1,9-nonanedioloxalate), poly(isoidide/1,10-decanediol oxalate),poly(isoidide/triethylene glycol oxalate) (also referred to aspoly(isoidide/dioxytriethylene oxalate)) and poly(isoidide/diethyleneglycol oxalate) (also referred to as poly(isoidide/oxydiethyleneoxalate)).

Such polyester copolymers preferably have a number average molecularweight of equal to or more than 5000 grams/mole and preferably has aglass transition temperature of less than 160° C., more preferably equalto or less than 140° C. Further preferences for number average molecularweight and glass transition temperature are as described previouslyherein for the polyester copolymers.

In the case of polyester copolymers comprising diethylene glycol-derivedmonomer units or triethylene glycol-derived monomer units, the polyestercopolymer does not only comprise a plurality of monomer units linked viaester functional groups in its main chain, but may suitably in additioncomprise the ether functional groups inside of such monomer units.

The polyester copolymer can suitably be combined with additives and/orother polymers and therefore the invention further provides acomposition containing a polyester copolymer according to the inventionand in addition one or more additives and/or one or more additional(other) polymers.

Such composition can for example comprise, as additive, nucleatingagents. These nucleating agents can be organic or inorganic in nature.Examples of nucleating agents are talc, calcium silicate, sodiumbenzoate, calcium titanate, boron nitride, zinc salts, porphyrins,chlorin and phlorin.

The composition according to the invention can also comprise, asadditive, nanometric (i.e. having particles of a nanometric size) ornon-nanometric and functionalized or non-functionalized fillers orfibres of organic or inorganic nature. They can be silicas, zeolites,glass fibres or beads, clays, mica, titanates, silicates, graphite,calcium carbonate, carbon nanotubes, wood fibres, carbon fibres, polymerfibres, proteins, cellulose fibres, lignocellulose fibres andnondestructured granular starch. These fillers or fibres can make itpossible to improve the hardness, the stiffness or the permeability towater or to gases. The composition can comprise from 0.1% to 75% byweight, for example from 0.5% to 50% by weight, of fillers and/orfibres, with respect to the total weight of the composition. Thecomposition can also be of composite type, that is to say can compriselarge amounts of these fillers and/or fibres.

The composition can also comprise, as additive, opacifying agents, dyesand pigments. They can be chosen from cobalt acetate and the followingcompounds: HS-325 Sandoplast® Red BB, which is a compound carrying anazo functional group also known under the name Solvent Red 195, HS-510Sandoplast® Blue 2B, which is an anthraquinone, Polysynthren® Blue R andClariant® RSB Violet.

The composition can also comprise, as additive, a processing aid forreducing the pressure in the processing device. A mould-release agent,which makes it possible to reduce the adhesion to the equipment forshaping the polyester, such as the moulds or the rollers of calenderingdevices, can also be used. These agents can be selected from fatty acidesters and amides, metal salts, soaps, paraffins or hydrocarbon waxes.Specific examples of these agents are zinc stearate, calcium stearate,aluminium stearate, stearamide, erucamide, behenamide, beeswax orCandelilla wax.

The composition can also comprise other additives, such as stabilizers,for example light stabilizers, UV stabilizers and heat stabilizers,fluidifying agents, flame retardants and antistats. It can also compriseprimary and/or secondary antioxidants. The primary antioxidant can be asterically hindered phenol, such as the compounds Hostanox® 0 3,Hostanox® 0 10, Hostanox® 0 16, Ultranox® 210, Ultranox®276, Dovernox®10, Dovernox® 76, Dovernox® 3114, Irganox® 1010 or Irganox® 1076. Thesecondary antioxidant can be trivalent phosphorous-comprising compounds,such as Ultranox® 626, Doverphos® S-9228 or Sandostab® P-EPQ.

In addition, the composition can comprise one or more additionalpolymers other than the one or more polyester copolymers according tothe invention. Such additional polymer(s) can suitably be chosen fromthe group consisting of polyamides, polystyrene, styrene copolymers,styrene/acrylonitrile copolymers, styrene/acrylonitrile/butadienecopolymers, polymethyl methacrylates, acrylic copolymers,poly(ether/imide)s, polyphenylene oxides, such aspoly(2,6-dimethylphenylene oxide), polyphenylene sulfide,poly(ester/carbonate)s, polycarbonates, polysulphones, polysulphoneethers, polyetherketones and blends of these polymers.

The composition can also comprise, as additional polymer, a polymerwhich makes it possible to improve the impact properties of the polymer,in particular functional polyolefins, such as functionalized polymersand copolymers of ethylene or propylene, core/shell copolymers or blockcopolymers.

The compositions according to the invention can also comprise, asadditional polymer(s), polymers of natural origin, such as starch,cellulose, chitosans, alginates, proteins, such as gluten, pea proteins,casein, collagen, gelatin or lignin, it being possible or not for thesepolymers of natural origin to be physically or chemically modified. Thestarch can be used in the destructured or plasticized form. In thelatter case, the plasticizer can be water or a polyol, in particularglycerol, polyglycerol, isosorbide, sorbitans, sorbitol, mannitol oralso urea. Use may in particular be made, in order to prepare thecomposition, of the process described in the document WO 2010/0102822A1.

The composition can suitably be manufactured by conventional methods forthe conversion of thermoplastics. These conventional methods maycomprise at least one stage of melt or softened blending of the polymersand one stage of recovery of the composition. Such blending can forexample be carried out in internal blade or rotor mixers, an externalmixer, or single-screw or co-rotating or counter-rotating twin-screwextruders. However, it is preferred to carry out this blending byextrusion, in particular by using a co-rotating extruder. The blendingof the constituents of the composition can suitably be carried out at atemperature ranging from 220 to 300° C., preferably under an inertatmosphere. In the case of an extruder, the various constituents of thecomposition can suitably be introduced using introduction hopperslocated along the extruder.

The invention also relates to an article comprising a polyestercopolymer according to the invention or a composition comprising apolyester copolymer according to the invention and one or more additivesand/or additional polymers. The polyester copolymer may conveniently beused in the manufacturing of films, fibres, injection moulded parts andpackaging materials, such as for example receptacles. As explainedabove, the use of the polyester copolymer is especially advantageouswhere such films, fibres, injection moulded parts or packaging materialsneed to be heat-resistant or cold-resistant

The article can also be a fibre for use in the textile industry. Thesefibres can be woven, in order to form fabrics, or also nonwoven.

The article can also be a film or a sheet. These films or sheets can bemanufactured by calendering, cast film extrusion or film blowingextrusion techniques. These films can be used for the manufacture oflabels or insulators.

This article can also be a receptacle, it being possible for thisreceptacle to be used for hot filling. This article can be manufacturedfrom the polyester copolymer or a composition comprising a polyestercopolymer and one or more additives and/or additional polymers usingconventional conversion techniques. The article can also be a receptaclefor transporting gases, liquids and/or solids. The receptacles concernedmay be baby's bottles, flasks, bottles, for example sparkling or stillwater bottles, juice bottles, soda bottles, carboys, alcoholic drinkbottles, medicine bottles or bottles for cosmetic products, dishes, forexample for ready-made meals or microwave dishes, or also lids. Thesereceptacles can be of any size.

The article may for example be suitably manufactured by extrusion-blowmoulding, thermoforming or injection-blow moulding.

The present invention therefore also conveniently provides a method formanufacturing an article, comprising the use of one or more polyestercopolymers according to the invention and preferably comprising thefollowing steps: 1) the provision of a polyester copolymer as describedabove; 2) melting the polyester copolymer, and optionally one or moreadditives and/or one or more additional polymers, to thereby produce apolymer melt; and 3) extrusion-blow moulding, thermoforming and/orinjection-blow moulding the polymer melt into the article.

The article can also be manufactured according to a process comprising astage of application of a layer of polyester in the molten state to alayer based on organic polymer, on metal or on adhesive composition inthe solid state. This stage can be carried out by pressing,overmoulding, lamination, extrusion-lamination, coating orextrusion-coating.

EXAMPLES

Analytical Methods:

In the below examples, the weight average molecular weight (Mw) and thenumber average molecular weight (Mn) have been determined by means ofgel permeation chromatography (GPC). GPC measurements were performed at25° C. For the calculation polystyrene standards were used. As eluent asolvent mixture of chloroform:2-chlorophenol 6:4 (vol/vol) was used. TheGPC measurements were carried out under these conditions on aMerck-Hitachi LaChrom HPLC system equipped with two PLgel 5 micrometer(μm) MIXED-C (300×7.5 mm) columns. Calculation of the molecular weightswas carried out with Cirrus™ PL DataStream software.

The glass transition temperature of the polyester polymers andcopolymers in the below examples was determined using differentialscanning calorimetry (DSC) with heating rate 10° C./minute in a nitrogenatmosphere. In the first heating cycle, a glass transition, (Tg), wasobserved.

The content of the monomer units in the polyester polymers andcopolymers of the below examples was determined by proton nuclearmagnetic resonance (¹H NMR). The content of diol monomer units wasdetermined using 1,2-dideutero-1,1,2,2-tetrachloroethane (TCE-d2) as asolvent, and 1,1,2,2-tetrachloroethane (TCE) as a reference. Peakassignments are set using the TCE-peak at a chemical shift of 6.04 ppm.The proton peak on C2 and C6 of isosorbide at chemical shifts of5.37-5.39 ppm is integrated and the integral is set at 1.000 for the twoprotons on C2 and C6 of isosorbide. The content of the linear C2-C12diols is determined from the integral (x) of the shifts at 4.31 to 4.48ppm, representing four protons. The content of linear C2-C12 diols inthe polyester polymers and copolymers can subsequently suitably becalculated as follows:linear C2-C12 diols content (mole %)=100*(x/4)/{2*((x/4)+(1/2))}.

Comparative Example 1: Preparation of an Poly(Isosorbide-Oxalate)Polyester Polymer by Polymerization of Isosorbide and Diphenyl Oxalate

14.62 gram (g) of isosorbide (to be abbreviated as ISO hereinafter,100.05 millimol (mmol), bio-sourced), 24.82 g of diphenyl oxalate (to beabbreviated as DPO hereinafter, 102.45 mmol, derived from carbonmonoxide), 8.3 milligram (mg) of Irganox 1010 and 9.2 mg Hostanox PEPQwere weighted into a 100 milliliter (mL) glass reactor equipped with amechanical stirrer, nitrogen gas inlet, a distillation head thatconnected the glass reactor to a condenser and a receiver to collect thecondensation products. The glass reactor was heated by means of an oilbath.

Transesterification and Pre-Polycondensation Stage:

The reactor contents were heated in a nitrogen atmosphere until theymelted (The exact melt temperature differed per example dependent on theexact type and amount of monomers, but in all examples a clear solutionwas formed at a temperature above 120° C.). As soon as the mixture meltwas obtained, 2.1 mg of n-butyltinhydroxideoxide (0.01 mmol) in toluenesolution were added as a catalyst. Subsequently the reactor contentswere heated further until a temperature of 195° C. was obtained (hereinit was assumed that the temperature of the reactor contents were equalto the temperature of the oil bath), and kept at such temperature for120 minutes. Thereafter, the degree of vacuum was adjusted to 400millibar (mbar) over 2 hours.

Polycondensation Stage:

The temperature was raised to 250° C. at a rate of 10° C./10 minutes andthe pressure was reduced to lower than 1 millibar (mbar) over 2 hours.Phenol and unreacted diol were removed by means of distillation toobtain a poly(isosorbide-oxalate) polyester polymer.

The obtained polyester polymer had a Tg, Mw, Mn and polydispersity index(PDI) as indicated in Table I.

Comparative Example 2: Preparation of an Poly(Isosorbide-Oxalate)Polyester Polymer by Polymerization of Isosorbide and Diethyl Oxalate

14.66 gram (g) of isosorbide (to be abbreviated as ISO hereinafter,100.21 millimol (mmol), bio-sourced), 15.83 g of diethyl oxalate (to beabbreviated as DEO hereinafter, 108.25 mmol, derived from carbonmonoxide), 14.3 milligram (mg) of Irganox 1010 and 9.2 mg Hostanox PEPQwere weighted into a 100 milliliter (mL) glass reactor equipped with amechanical stirrer, nitrogen gas inlet, a distillation head thatconnected the glass reactor to a condenser and a receiver to collect thecondensation products. The glass reactor was heated by means of an oilbath.

Transesterification and Pre-Polycondensation Stage:

The reactor contents were heated in a nitrogen atmosphere until theydissolved. As soon as a clear solution was obtained, 2.1 mg ofn-butyltinhydroxideoxide (0.01 mmol) in toluene solution were added as acatalyst. Subsequently the reactor contents were heated further until atemperature of 180° C. was obtained (herein it was assumed that thetemperature of the reactor contents were equal to the temperature of theoil bath), and kept at such temperature for 480 minutes. Thereafter, thedegree of vacuum was adjusted to 400 millibar (mbar) over 2 hours.

Polycondensation Stage:

The temperature was raised to 250° C. at a rate of 10° C./10 minutes andthe pressure was reduced to lower than 1 millibar (mbar) over 2 hours,then continued another 4 hours to obtain a dark-coloured,poly(isosorbide-oxalate) polyester polymer.

The obtained polyester polymer had a weight average molecular weight(Mw) of 3200, a number average molecular weight (Mn) of 1700 andpolydispersity index (PDI=1.88) as indicated in Table I.

Comparative Example 3: Preparation of an Poly(Isosorbide-Oxalate)Polyester Polymer by Polymerization of Isosorbide and Oxalic Acid

14.61 gram (g) of isosorbide (to be abbreviated as ISO hereinafter,99.91 millimol (mmol), bio-sourced), 9.03 g of oxalic acid (to beabbreviated as OA hereinafter, 100.03 mmol), were weighted into a 100milliliter (mL) glass reactor equipped with a mechanical stirrer,nitrogen gas inlet, a distillation head that connected the glass reactorto a condenser and a receiver to collect the condensation products. Theglass reactor was heated by means of an oil bath.

Transesterification and Pre-Polycondensation Stage:

The reactor contents were heated in a nitrogen atmosphere until theymelt at 100° C. As soon as a clear solution was obtained, 2.1 mg ofn-butyltinhydroxideoxide (0.01 mmol) in toluene solution were added as acatalyst. Subsequently the reactor contents were heated further until atemperature of 150° C. was obtained (herein it was assumed that thetemperature of the reactor contents were 10° C. lower than thetemperature of the oil bath), and kept at such temperature for 360minutes. Thereafter, the degree of vacuum was adjusted to 400 millibar(mbar) over 2 hours.

Polycondensation Stage:

The temperature was raised to 230° C. at a rate of 10° C./10 minutes andthe pressure was reduced to lower than 1 millibar (mbar) over 2 hours,then continued another 3 hours to obtain a dark viscous liquidcontaining merely very low molecular weight polymers of which themolecular weight could not be determined.

Comparative examples 2 and 3 illustrate that when using oxalic acid ordiethyloxalate it is not possible to obtain a polyester polymer with acommercially interesting molecular weight.

Example 4: Preparation of Poly(Isosorbide/Butylene Oxalate) PolyesterCopolymer by Polymerization of Diphenyl Oxalate, Isosorbide andButanediol-1,4

Example 4 was carried out as example 1, except that 12.47 g ofisosorbide (to be abbreviated as ISO hereinafter, 85.31 mmol), 25.50 gof diphenyl oxalate (to be abbreviated as DPO hereinafter, 105.31 mmol),1.80 g of butanediol-1,4 (to be abbreviated as BDO hereinafter, 19.96mmol), 8.3 mg of Irganox 1010 and 9.2 mg Hostanox PEPQ were weightedinto the 100 mL glass reactor. In the polycondensation stage thepressure was reduced to lower than 1 mbar over 1.5 hours instead of over2 hours. The resulting poly(isosorbide/butylene oxalate) polyestercopolymer contained 8.7 mole % butanediol monomer units in the polyestercopolymer, and had a Tg, Mw, Mn and polydispersity index as indicated inTable I.

Example 5: Preparation of Poly(Isosorbide/Butylene Oxalate) PolyesterCopolymer by Polymerization of Diphenyl Oxalate, Isosorbide andButanediol-1,4

Example 5 was carried out as comparative example 1, except that 7.68 gof isosorbide (to be abbreviated as ISO hereinafter, 52.51 mmol), 25.82g of diphenyl oxalate (to be abbreviated as DPO hereinafter, 106.61mmol), 4.85 g of butanediol-1,4 (to be abbreviated as BDO hereinafter,53.80 mmol), 9.4 mg of Irganox 1010 and 12.1 mg Hostanox PEPQ wereweighted into the 100 mL glass reactor.

In the polycondensation stage the pressure was reduced to lower than 5mbar (instead of the 1 mbar mentioned in example 1) over 1.5 hours. Theresulting poly(isosorbide/butylene oxalate) polyester copolymercontained 23.7 mole % butanediol monomer units in the polyestercopolymer and had a Tg, Mw, Mn and polydispersity index as indicated inTable I.

Example 6: Preparation of Poly(Isosorbide/Butylene Oxalate) PolyesterCopolymer by Polymerization of Diphenyl Oxalate, Isosorbide andButanediol-1,4

Example 6 was carried out as example 5, except that 10.50 g ofisosorbide (to be abbreviated as ISO hereinafter, 71.81 mmol), 25.49 gof diphenyl oxalate (to be abbreviated as DPO hereinafter, 105.23 mmol),2.94 g of butanediol-1,4 (to be abbreviated as BDO hereinafter, 32.65mmol), 9.1 mg of Irganox 1010 and 9.8 mg Hostanox PEPQ were weightedinto the 100 mL glass reactor. The resulting poly(isosorbide/butyleneoxalate) polyester copolymer contained 13.8 mole % butanediol monomerunits in the polyester copolymer and had a Tg, Mw, Mn and polydispersityindex as indicated in Table I.

Example 7: Preparation of Poly(Isosorbide/Butylene Oxalate) PolyesterCopolymer by Polymerization of Diphenyl Oxalate, Isosorbide andButanediol-1,4

Example 7 was carried out as example 5, except that 12.43 g ofisosorbide (to be abbreviated as ISO hereinafter, 85.03 mmol), 25.50 gof diphenyl oxalate (to be abbreviated as DPO hereinafter, 105.27 mmol),1.70 g of butanediol-1,4 (to be abbreviated as BDO hereinafter, 18.84mmol), 10.6 mg of Irganox 1010 and 10.0 mg Hostanox PEPQ were weightedinto the 100 mL glass reactor.

The resulting poly(isosorbide/butylene oxalate) polyester copolymercontained 7.7 mole % butanediol monomer units in the polyester copolymerand had a Tg, Mw, Mn and polydispersity index as indicated in Table I.

Example 8: Preparation of Poly(Isosorbide/Triethylene Glycol Oxalate)Polyester Copolymer by Polymerization of Diphenyl Oxalate, Isosorbideand Triethylene Glycol (TEG)

Example 8 was carried out as comparative example 1, except that 12.92 gof isosorbide (to be abbreviated as ISO hereinafter, 88.37 mmol), 25.51g of diphenyl oxalate (to be abbreviated as DPO hereinafter, 105.33mmol), 2.38 g of triethylene glycol (to be abbreviated as TEGhereinafter, 15.82 mmol), 8.5 mg of Irganox 1010 and 10.0 mg HostanoxPEPQ were weighted into the 100 mL glass reactor.

In the polycondensation stage the temperature was raised to 235° C. in1° C./min (instead of the 250° C. at a rate of 10° C./10 minutesmentioned for example 1) and the pressure was reduced to lower than 1mbar over 1.5 hours (instead of the 2 hours mentioned for example 1).The resulting poly(isosorbide/triethylene oxalate) polyester copolymercontained 7.6 mole % TEG monomer units in the polyester copolymer andhad a Tg, Mw, Mn and polydispersity index as indicated in Table I.

Example 9: Preparation of Poly(Isosorbide/Hexamethylene Oxalate)Polyester Copolymer by Polymerization of Diphenyl Oxalate, Isosorbideand Hexane-1,6-Diol

Example 9 was carried out as example 8, except that 12.50 g ofisosorbide (to be abbreviated as ISO hereinafter, 85.53 mmol), 26.09 gof diphenyl oxalate (to be abbreviated as DPO hereinafter, 107.69 mmol),2.51 g of Hexanediol-1,6 (to be abbreviated as HDO hereinafter, 21.26mmol), 8.3 mg of Irganox 1010 and 8.6 mg Hostanox PEPQ were weightedinto the 100 mL glass reactor.

The resulting poly(isosorbide/hexamethylene oxalate) polyester copolymercontained 9.8 mole % hexanediol monomer units in the polyester copolymerand had a Tg, Mw, Mn and polydispersity index as indicated in Table I.

Example 10: Preparation of Poly(Isosorbide/Diethylene Glycol Oxalate)Polyester Copolymer by Polymerization of Diphenyl Oxalate, Isosorbideand Diethyleneglycol (DEG)

Example 10 was carried out as example 8, except that 11.50 g ofisosorbide (to be abbreviated as ISO hereinafter, 78.69 mmol), 26.06 gof diphenyl oxalate (to be abbreviated as DPO hereinafter, 107.59 mmol),2.97 g of diethylene glycol (to be abbreviated as DEG hereinafter, 28.02mmol), 7.9 mg of Irganox 1010 and 9.1 mg Hostanox PEPQ were weightedinto the 100 mL glass reactor.

In the polycondensation stage the temperature was raised to 235° C. in1° C./min (instead of the 225° C. mentioned for example 6) and thepressure was reduced to lower than 1 mbar over 1.5 hours.

The resulting poly(isosorbide/diethylene oxalate) polyester copolymercontained 13.1 mole % DEG monomer units in the polyester copolymer andhad a Tg, Mw, Mn and polydispersity index as indicated in Table I.

In the below Table I:

ISO=Isosorbide

DEO=Diethyloxalate

OA=Oxalic acid

DPO=Diphenyloxalate

BDO=Butane-1,4-diol

HDO=Hexane-1,6-diol

DEG=Diethyleneglycol

TEG=Triethyleneglycol

PDI=polydispersity index

Mw=weight average molecular weight

Mn=number average molecular weight

Tg=glass transition temperature ISO:lin.C2-C12 diol molar ratio=ISOmonomer:linear C2-C12 diol monomer molar ratio. This molar ratio isexpected to be representative for the molar ratio of isosorbide oxalaterepeating units to linear C2-C12 diol-oxalate repeating units in theresulting polyester copolymer.

Mole % lin. C2-C12 diol in polymer=linear C2-C12 diol monomer unit molepercentage in the resulting polymer (mole %).

TABLE I Monomers used and properties of the resulting polyestercopolymer ISO in Oxalic diester or oxalic Linear C2-C12 ISO:lin.C2- Mole% linear the feed acid in the feed Diol in the feed C12 diol C2-C12 diolTg Mn Mw Example (mmol) (mmol) (mmol) molar ratio in polymer (° C.)(g/mol) (g/mol) PDI  1* 100.05 DPO 102.45 n.a. n.a. n.a. n.a. 165 1290026500 2.05  2* 100.21 DEO 108.25 n.a. n.a. n.a. n.a. 91  1700  3200 1.88 3* 99.91 OA 100.03 n.a. n.a. n.a. n.a. n.d. Very low Very low n.d. 485.31 DPO 105.31 BDO 19.96 4.3 8.7 131 17900 39600 2.22 5 52.51 DPO106.61 BDO 53.80 1.0 23.7 68 12500 27000 2.16 6 71.81 DPO 105.23 BDO32.65 2.2 13.8 105 12800 24200 1.89 7 85.03 DPO 105.27 BDO 18.84 4.5 7.7130 13200 27200 2.06 8 88.37 DPO 105.33 TEG 15.82 5.6 7.6 117 1350028600 2.11 9 85.53 DPO 107.69 HDO 21.26 4.0 9.8 114 20287 41949 2.07 10 78.69 DPO 107.59 DEG 28.02 2.8 13.1 108 17300 42200 2.44 In all examples0.01 mmol of n-butyltinhydroxideoxide catalyst was used. n.a. = notapplicable; n.d. = not determined; *indicates a comparative example.

The invention claimed is:
 1. A polyester copolymer having a numberaverage molecular weight of equal to or more than 5000 grams/mole andhaving a glass transition temperature of less than 160° C., comprising:in the range from equal to or more than 25.0 mole % to equal to or lessthan 49.9 mole %, based on the total amount of moles of monomer unitswithin the polyester copolymer, of one or more bicyclic diol monomerunits derived from one or more bicyclic diols chosen from the groupconsisting of isosorbide, isoidide, isomannide,2,3:4,5-di-O-methylene-galactitol and 2,4:3,5-di-O-methylene-D-mannitol;and/or in the range from equal to or more than 45.0 mole % to equal toor less than 50.0 mole %, based on the total amount of moles of monomerunits within the polyester copolymer, of an oxalate monomer unit; and/orin the range from equal to or more than 0.1 mole % to equal to or lessthan 25.0 mole %, based on the total amount of moles of monomer unitswithin the polyester copolymer, of one or more linear C2-C12 diolmonomer units derived from one or more linear C2-C12 diols; and/oroptionally equal to or more than 0.0 mole % to equal to or less than 5.0mole %, based on the total amount of moles of monomer units within thepolyester copolymer, of the one or more additional monomer units.
 2. Thepolyester copolymer according to claim 1, comprising in the range fromequal to or more than 1 mole % based on the total amount of moles ofmonomer units within the polyester copolymer, of the one or more linearC2-C12 diol monomer units.
 3. The polyester copolymer according to claim1, wherein the one or more bicyclic diol monomer units is/are one ormore 1,4:3,6-dianhydrohexitols monomer units.
 4. The polyester copolymeraccording to claim 3, wherein the one or more 1,4:3,6-dianhydrohexitolmonomer units is/are derived from isosorbide and/or isoidide.
 5. Apolyester copolymer, having a number average molecular weight of equalto or more than 5000 grams/mole and having a glass transitiontemperature of less than 160° C., comprising the following repeatingunits: in the range from equal to or more than 45.0 mole % to equal toor less than 99.9 mole %, based on the total amount of moles ofrepeating units within the polyester copolymer, of one or more bicyclicdiol-oxalate repeating units chosen from the group consisting ofisosorbide-oxalate, isoidide-oxalate, isomannide-oxalate,2,3:4,5-di-O-methylene-galactitol-oxalate and2,4:3,5-di-O-methylene-D-mannitol-oxalate; in the range from equal to ormore than 0.1 mole % to equal to or less than 50.0 mole %, based on thetotal amount of moles of repeating units within the polyester copolymer,of one or more linear C2-C12-diol oxalate repeating units; optionally inthe range from equal to or more than 0.0 mole % to equal to or less than5.0 mole %, based on the total amount of moles of repeating units withinthe polyester copolymer, of one or more additional repeating units;wherein the molar ratio of bicyclic diol-oxalate repeating units tolinear C2-C12-diol oxalate repeating units is equal to or more than 1:1,more preferably equal to or more than 1.5:1.
 6. The polyester copolymeraccording to claim 5, wherein the polyester copolymer has a glasstransition temperature in the range from equal to or more than minus 20°C. (−20° C.) to equal to or less than 100° C.
 7. The polyester copolymeraccording to claim 5, wherein the polyester copolymer has a glasstransition temperature in the range from equal to or more than 80° C. toless than 160° C.
 8. The polyester copolymer according to claim 5,wherein the polyester copolymer has a glass transition temperature ofequal to or less than 140° C.
 9. The polyester copolymer according toclaim 5, wherein the polyester copolymer has a number average molecularweight in the range from equal to or more than 9000 grams/mole to equalto or less than 150000 grams/mole.
 10. A process for the production of apolyester copolymer, comprising polymerizing the following monomers: inthe range from equal to or more than 25.0 mole % to equal to or lessthan 49.9 mole %, based on the total amount of moles of monomers, of oneor more bicyclic diols chosen from the group consisting of isosorbide,isoidide, isomannide, 2,3:4,5-di-O-methylene-galactitol and2,4:3,5-di-O-methylene-D-mannitol; in the range from equal to or morethan 45.0 mole % to equal to or less than 50.0 mole %, based on thetotal amount of moles of monomers, of the one or more oxalic diestershaving a chemical structure according to formula (VI):

wherein R₂ and R₃ each independently are a C3-C20 alkyl group, a C2-C20alkenyl group, a C4-C20 cycloalkyl group, a C4-C20 aryl group or aC5-C20 alkylaryl group; in the range from equal to or more than 0.1 mole% to equal to or less than 25.0 mole %, based on the total amount ofmoles of monomers, of one or more linear C2-C12 diols; and optionallyequal to or more than 0.0 mole % to equal to or less than 5.0 mole %,based on the total amount of moles of monomers, of the one or moreadditional monomers.
 11. The process according to claim 10, wherein theone or more bicyclic diols is/are first reacted with the one or moreoxalic diesters in the presence of a metal-containing catalyst underpolymerization conditions to produce a bicyclic diol-oxalate esterproduct, whereafter the bicyclic diol-oxalate ester product issubsequently reacted with the one or more linear C2-C12 diols in thepresence of a metal-containing catalyst under further polymerizationconditions to produce the polyester copolymer.
 12. The process accordingto claim 10, wherein the one or more oxalic diesters are one or moreoxalic diesters having a chemical structure according to formula (VI):

wherein R₂ and R₃ each independently are a C2-C20 alkenyl group.
 13. Theprocess according to claim 10, wherein at least one of R₂ and R₃ arechosen from the group consisting of vinyl, allyl and 1-propenyl.
 14. Theprocess according to claim 10, wherein the one or more linear C2-C12diols have a chemical structure according to formula (VII):—HO—R₁—OH  (VII) wherein R₁ is a linear organic group.
 15. The polyestercopolymer according to claim 3, wherein the molar ratio of1,4:3,6-dianhydrohexitols monomer units to linear C2-C12 diol monomerunits is equal to or more than 1:1.
 16. The process according to claim14, wherein R₁ is an alkylene group with structure —[CH₂]_(n)—, whereinn represents the number of —[CH₂]— units and wherein n is a number inthe range from 1 to 10.